Adding upstream version 4.22.0.upstream/4.22.0

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 3014 insertions, 0 deletions

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+.\" -*- mode: troff; coding: utf-8 -*-
+.\" Automatically generated by Pod::Man 5.01 (Pod::Simple 3.43)
+.\"
+.\" Standard preamble:
+.\" ========================================================================
+.de Sp \" Vertical space (when we can't use .PP)
+.if t .sp .5v
+.if n .sp
+..
+.de Vb \" Begin verbatim text
+.ft CW
+.nf
+.ne \\$1
+..
+.de Ve \" End verbatim text
+.ft R
+.fi
+..
+.\" \*(C` and \*(C' are quotes in nroff, nothing in troff, for use with C<>.
+.ie n \{\
+.    ds C` ""
+.    ds C' ""
+'br\}
+.el\{\
+.    ds C`
+.    ds C'
+'br\}
+.\"
+.\" Escape single quotes in literal strings from groff's Unicode transform.
+.ie \n(.g .ds Aq \(aq
+.el       .ds Aq '
+.\"
+.\" If the F register is >0, we'll generate index entries on stderr for
+.\" titles (.TH), headers (.SH), subsections (.SS), items (.Ip), and index
+.\" entries marked with X<> in POD.  Of course, you'll have to process the
+.\" output yourself in some meaningful fashion.
+.\"
+.\" Avoid warning from groff about undefined register 'F'.
+.de IX
+..
+.nr rF 0
+.if \n(.g .if rF .nr rF 1
+.if (\n(rF:(\n(.g==0)) \{\
+.    if \nF \{\
+.        de IX
+.        tm Index:\\$1\t\\n%\t"\\$2"
+..
+.        if !\nF==2 \{\
+.            nr % 0
+.            nr F 2
+.        \}
+.    \}
+.\}
+.rr rF
+.\" ========================================================================
+.\"
+.IX Title "PERL5180DELTA 1"
+.TH PERL5180DELTA 1 2023-11-28 "perl v5.38.2" "Perl Programmers Reference Guide"
+.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
+.\" way too many mistakes in technical documents.
+.if n .ad l
+.nh
+.SH NAME
+perl5180delta \- what is new for perl v5.18.0
+.SH DESCRIPTION
+.IX Header "DESCRIPTION"
+This document describes differences between the v5.16.0 release and the v5.18.0
+release.
+.PP
+If you are upgrading from an earlier release such as v5.14.0, first read
+perl5160delta, which describes differences between v5.14.0 and v5.16.0.
+.SH "Core Enhancements"
+.IX Header "Core Enhancements"
+.SS "New mechanism for experimental features"
+.IX Subsection "New mechanism for experimental features"
+Newly-added experimental features will now require this incantation:
+.PP
+.Vb 2
+\&    no warnings "experimental::feature_name";
+\&    use feature "feature_name";  # would warn without the prev line
+.Ve
+.PP
+There is a new warnings category, called "experimental", containing
+warnings that the feature pragma emits when enabling experimental
+features.
+.PP
+Newly-added experimental features will also be given special warning IDs,
+which consist of "experimental::" followed by the name of the feature.  (The
+plan is to extend this mechanism eventually to all warnings, to allow them
+to be enabled or disabled individually, and not just by category.)
+.PP
+By saying
+.PP
+.Vb 1
+\&    no warnings "experimental::feature_name";
+.Ve
+.PP
+you are taking responsibility for any breakage that future changes to, or
+removal of, the feature may cause.
+.PP
+Since some features (like \f(CW\*(C`~~\*(C'\fR or \f(CW\*(C`my $_\*(C'\fR) now emit experimental warnings,
+and you may want to disable them in code that is also run on perls that do not
+recognize these warning categories, consider using the \f(CW\*(C`if\*(C'\fR pragma like this:
+.PP
+.Vb 1
+\&    no if $] >= 5.018, warnings => "experimental::feature_name";
+.Ve
+.PP
+Existing experimental features may begin emitting these warnings, too.  Please
+consult perlexperiment for information on which features are considered
+experimental.
+.SS "Hash overhaul"
+.IX Subsection "Hash overhaul"
+Changes to the implementation of hashes in perl v5.18.0 will be one of the most
+visible changes to the behavior of existing code.
+.PP
+By default, two distinct hash variables with identical keys and values may now
+provide their contents in a different order where it was previously identical.
+.PP
+When encountering these changes, the key to cleaning up from them is to accept
+that \fBhashes are unordered collections\fR and to act accordingly.
+.PP
+\fIHash randomization\fR
+.IX Subsection "Hash randomization"
+.PP
+The seed used by Perl's hash function is now random.  This means that the
+order which keys/values will be returned from functions like \f(CWkeys()\fR,
+\&\f(CWvalues()\fR, and \f(CWeach()\fR will differ from run to run.
+.PP
+This change was introduced to make Perl's hashes more robust to algorithmic
+complexity attacks, and also because we discovered that it exposes hash
+ordering dependency bugs and makes them easier to track down.
+.PP
+Toolchain maintainers might want to invest in additional infrastructure to
+test for things like this.  Running tests several times in a row and then
+comparing results will make it easier to spot hash order dependencies in
+code.  Authors are strongly encouraged not to expose the key order of
+Perl's hashes to insecure audiences.
+.PP
+Further, every hash has its own iteration order, which should make it much
+more difficult to determine what the current hash seed is.
+.PP
+\fINew hash functions\fR
+.IX Subsection "New hash functions"
+.PP
+Perl v5.18 includes support for multiple hash functions, and changed
+the default (to ONE_AT_A_TIME_HARD), you can choose a different
+algorithm by defining a symbol at compile time.  For a current list,
+consult the \fIINSTALL\fR document.  Note that as of Perl v5.18 we can
+only recommend use of the default or SIPHASH. All the others are
+known to have security issues and are for research purposes only.
+.PP
+\fIPERL_HASH_SEED environment variable now takes a hex value\fR
+.IX Subsection "PERL_HASH_SEED environment variable now takes a hex value"
+.PP
+\&\f(CW\*(C`PERL_HASH_SEED\*(C'\fR no longer accepts an integer as a parameter;
+instead the value is expected to be a binary value encoded in a hex
+string, such as "0xf5867c55039dc724".  This is to make the
+infrastructure support hash seeds of arbitrary lengths, which might
+exceed that of an integer.  (SipHash uses a 16 byte seed.)
+.PP
+\fIPERL_PERTURB_KEYS environment variable added\fR
+.IX Subsection "PERL_PERTURB_KEYS environment variable added"
+.PP
+The \f(CW\*(C`PERL_PERTURB_KEYS\*(C'\fR environment variable allows one to control the level of
+randomization applied to \f(CW\*(C`keys\*(C'\fR and friends.
+.PP
+When \f(CW\*(C`PERL_PERTURB_KEYS\*(C'\fR is 0, perl will not randomize the key order at all. The
+chance that \f(CW\*(C`keys\*(C'\fR changes due to an insert will be the same as in previous
+perls, basically only when the bucket size is changed.
+.PP
+When \f(CW\*(C`PERL_PERTURB_KEYS\*(C'\fR is 1, perl will randomize keys in a non-repeatable
+way. The chance that \f(CW\*(C`keys\*(C'\fR changes due to an insert will be very high.  This
+is the most secure and default mode.
+.PP
+When \f(CW\*(C`PERL_PERTURB_KEYS\*(C'\fR is 2, perl will randomize keys in a repeatable way.
+Repeated runs of the same program should produce the same output every time.
+.PP
+\&\f(CW\*(C`PERL_HASH_SEED\*(C'\fR implies a non-default \f(CW\*(C`PERL_PERTURB_KEYS\*(C'\fR setting. Setting
+\&\f(CW\*(C`PERL_HASH_SEED=0\*(C'\fR (exactly one 0) implies \f(CW\*(C`PERL_PERTURB_KEYS=0\*(C'\fR (hash key
+randomization disabled); setting \f(CW\*(C`PERL_HASH_SEED\*(C'\fR to any other value implies
+\&\f(CW\*(C`PERL_PERTURB_KEYS=2\*(C'\fR (deterministic and repeatable hash key randomization).
+Specifying \f(CW\*(C`PERL_PERTURB_KEYS\*(C'\fR explicitly to a different level overrides this
+behavior.
+.PP
+\fR\f(BIHash::Util::hash_seed()\fR\fI now returns a string\fR
+.IX Subsection "Hash::Util::hash_seed() now returns a string"
+.PP
+\&\fBHash::Util::hash_seed()\fR now returns a string instead of an integer.  This
+is to make the infrastructure support hash seeds of arbitrary lengths
+which might exceed that of an integer.  (SipHash uses a 16 byte seed.)
+.PP
+\fIOutput of PERL_HASH_SEED_DEBUG has been changed\fR
+.IX Subsection "Output of PERL_HASH_SEED_DEBUG has been changed"
+.PP
+The environment variable PERL_HASH_SEED_DEBUG now makes perl show both the
+hash function perl was built with, \fIand\fR the seed, in hex, in use for that
+process. Code parsing this output, should it exist, must change to accommodate
+the new format.  Example of the new format:
+.PP
+.Vb 2
+\&    $ PERL_HASH_SEED_DEBUG=1 ./perl \-e1
+\&    HASH_FUNCTION = MURMUR3 HASH_SEED = 0x1476bb9f
+.Ve
+.SS "Upgrade to Unicode 6.2"
+.IX Subsection "Upgrade to Unicode 6.2"
+Perl now supports Unicode 6.2.  A list of changes from Unicode
+6.1 is at <http://www.unicode.org/versions/Unicode6.2.0>.
+.SS "Character name aliases may now include non\-Latin1\-range characters"
+.IX Subsection "Character name aliases may now include non-Latin1-range characters"
+It is possible to define your own names for characters for use in
+\&\f(CW\*(C`\eN{...}\*(C'\fR, \f(CWcharnames::vianame()\fR, etc.  These names can now be
+comprised of characters from the whole Unicode range.  This allows for
+names to be in your native language, and not just English.  Certain
+restrictions apply to the characters that may be used (you can't define
+a name that has punctuation in it, for example).  See "CUSTOM
+ALIASES" in charnames.
+.SS "New DTrace probes"
+.IX Subsection "New DTrace probes"
+The following new DTrace probes have been added:
+.IP \(bu 4
+\&\f(CW\*(C`op\-entry\*(C'\fR
+.IP \(bu 4
+\&\f(CW\*(C`loading\-file\*(C'\fR
+.IP \(bu 4
+\&\f(CW\*(C`loaded\-file\*(C'\fR
+.ie n .SS """${^LAST_FH}"""
+.el .SS \f(CW${^LAST_FH}\fP
+.IX Subsection "${^LAST_FH}"
+This new variable provides access to the filehandle that was last read.
+This is the handle used by \f(CW$.\fR and by \f(CW\*(C`tell\*(C'\fR and \f(CW\*(C`eof\*(C'\fR without
+arguments.
+.SS "Regular Expression Set Operations"
+.IX Subsection "Regular Expression Set Operations"
+This is an \fBexperimental\fR feature to allow matching against the union,
+intersection, etc., of sets of code points, similar to
+Unicode::Regex::Set.  It can also be used to extend \f(CW\*(C`/x\*(C'\fR processing
+to [bracketed] character classes, and as a replacement of user-defined
+properties, allowing more complex expressions than they do.  See
+"Extended Bracketed Character Classes" in perlrecharclass.
+.SS "Lexical subroutines"
+.IX Subsection "Lexical subroutines"
+This new feature is still considered \fBexperimental\fR.  To enable it:
+.PP
+.Vb 3
+\&    use 5.018;
+\&    no warnings "experimental::lexical_subs";
+\&    use feature "lexical_subs";
+.Ve
+.PP
+You can now declare subroutines with \f(CW\*(C`state sub foo\*(C'\fR, \f(CW\*(C`my sub foo\*(C'\fR, and
+\&\f(CW\*(C`our sub foo\*(C'\fR.  (\f(CW\*(C`state sub\*(C'\fR requires that the "state" feature be
+enabled, unless you write it as \f(CW\*(C`CORE::state sub foo\*(C'\fR.)
+.PP
+\&\f(CW\*(C`state sub\*(C'\fR creates a subroutine visible within the lexical scope in which
+it is declared.  The subroutine is shared between calls to the outer sub.
+.PP
+\&\f(CW\*(C`my sub\*(C'\fR declares a lexical subroutine that is created each time the
+enclosing block is entered.  \f(CW\*(C`state sub\*(C'\fR is generally slightly faster than
+\&\f(CW\*(C`my sub\*(C'\fR.
+.PP
+\&\f(CW\*(C`our sub\*(C'\fR declares a lexical alias to the package subroutine of the same
+name.
+.PP
+For more information, see "Lexical Subroutines" in perlsub.
+.SS "Computed Labels"
+.IX Subsection "Computed Labels"
+The loop controls \f(CW\*(C`next\*(C'\fR, \f(CW\*(C`last\*(C'\fR and \f(CW\*(C`redo\*(C'\fR, and the special \f(CW\*(C`dump\*(C'\fR
+operator, now allow arbitrary expressions to be used to compute labels at run
+time.  Previously, any argument that was not a constant was treated as the
+empty string.
+.SS "More CORE:: subs"
+.IX Subsection "More CORE:: subs"
+Several more built-in functions have been added as subroutines to the
+CORE:: namespace \- namely, those non-overridable keywords that can be
+implemented without custom parsers: \f(CW\*(C`defined\*(C'\fR, \f(CW\*(C`delete\*(C'\fR, \f(CW\*(C`exists\*(C'\fR,
+\&\f(CW\*(C`glob\*(C'\fR, \f(CW\*(C`pos\*(C'\fR, \f(CW\*(C`prototype\*(C'\fR, \f(CW\*(C`scalar\*(C'\fR, \f(CW\*(C`split\*(C'\fR, \f(CW\*(C`study\*(C'\fR, and \f(CW\*(C`undef\*(C'\fR.
+.PP
+As some of these have prototypes, \f(CWprototype(\*(AqCORE::...\*(Aq)\fR has been
+changed to not make a distinction between overridable and non-overridable
+keywords.  This is to make \f(CWprototype(\*(AqCORE::pos\*(Aq)\fR consistent with
+\&\f(CWprototype(&CORE::pos)\fR.
+.ie n .SS """kill"" with negative signal names"
+.el .SS "\f(CWkill\fP with negative signal names"
+.IX Subsection "kill with negative signal names"
+\&\f(CW\*(C`kill\*(C'\fR has always allowed a negative signal number, which kills the
+process group instead of a single process.  It has also allowed signal
+names.  But it did not behave consistently, because negative signal names
+were treated as 0.  Now negative signals names like \f(CW\*(C`\-INT\*(C'\fR are supported
+and treated the same way as \-2 [perl #112990].
+.SH Security
+.IX Header "Security"
+.SS "See also: hash overhaul"
+.IX Subsection "See also: hash overhaul"
+Some of the changes in the hash overhaul were made to
+enhance security.  Please read that section.
+.ie n .SS """Storable"" security warning in documentation"
+.el .SS "\f(CWStorable\fP security warning in documentation"
+.IX Subsection "Storable security warning in documentation"
+The documentation for \f(CW\*(C`Storable\*(C'\fR now includes a section which warns readers
+of the danger of accepting Storable documents from untrusted sources. The
+short version is that deserializing certain types of data can lead to loading
+modules and other code execution. This is documented behavior and wanted
+behavior, but this opens an attack vector for malicious entities.
+.ie n .SS """Locale::Maketext"" allowed code injection via a malicious template"
+.el .SS "\f(CWLocale::Maketext\fP allowed code injection via a malicious template"
+.IX Subsection "Locale::Maketext allowed code injection via a malicious template"
+If users could provide a translation string to Locale::Maketext, this could be
+used to invoke arbitrary Perl subroutines available in the current process.
+.PP
+This has been fixed, but it is still possible to invoke any method provided by
+\&\f(CW\*(C`Locale::Maketext\*(C'\fR itself or a subclass that you are using. One of these
+methods in turn will invoke the Perl core's \f(CW\*(C`sprintf\*(C'\fR subroutine.
+.PP
+In summary, allowing users to provide translation strings without auditing
+them is a bad idea.
+.PP
+This vulnerability is documented in CVE\-2012\-6329.
+.SS "Avoid calling memset with a negative count"
+.IX Subsection "Avoid calling memset with a negative count"
+Poorly written perl code that allows an attacker to specify the count to perl's
+\&\f(CW\*(C`x\*(C'\fR string repeat operator can already cause a memory exhaustion
+denial-of-service attack. A flaw in versions of perl before v5.15.5 can escalate
+that into a heap buffer overrun; coupled with versions of glibc before 2.16, it
+possibly allows the execution of arbitrary code.
+.PP
+The flaw addressed to this commit has been assigned identifier CVE\-2012\-5195
+and was researched by Tim Brown.
+.SH "Incompatible Changes"
+.IX Header "Incompatible Changes"
+.SS "See also: hash overhaul"
+.IX Subsection "See also: hash overhaul"
+Some of the changes in the hash overhaul are not fully
+compatible with previous versions of perl.  Please read that section.
+.ie n .SS "An unknown character name in ""\eN{...}"" is now a syntax error"
+.el .SS "An unknown character name in \f(CW\eN{...}\fP is now a syntax error"
+.IX Subsection "An unknown character name in N{...} is now a syntax error"
+Previously, it warned, and the Unicode REPLACEMENT CHARACTER was
+substituted.  Unicode now recommends that this situation be a syntax
+error.  Also, the previous behavior led to some confusing warnings and
+behaviors, and since the REPLACEMENT CHARACTER has no use other than as
+a stand-in for some unknown character, any code that has this problem is
+buggy.
+.ie n .SS "Formerly deprecated characters in ""\eN{}"" character name aliases are now errors."
+.el .SS "Formerly deprecated characters in \f(CW\eN{}\fP character name aliases are now errors."
+.IX Subsection "Formerly deprecated characters in N{} character name aliases are now errors."
+Since v5.12.0, it has been deprecated to use certain characters in
+user-defined \f(CW\*(C`\eN{...}\*(C'\fR character names.  These now cause a syntax
+error.  For example, it is now an error to begin a name with a digit,
+such as in
+.PP
+.Vb 1
+\& my $undraftable = "\eN{4F}";    # Syntax error!
+.Ve
+.PP
+or to have commas anywhere in the name.  See "CUSTOM ALIASES" in charnames.
+.ie n .SS """\eN{BELL}"" now refers to U+1F514 instead of U+0007"
+.el .SS "\f(CW\eN{BELL}\fP now refers to U+1F514 instead of U+0007"
+.IX Subsection "N{BELL} now refers to U+1F514 instead of U+0007"
+Unicode 6.0 reused the name "BELL" for a different code point than it
+traditionally had meant.  Since Perl v5.14, use of this name still
+referred to U+0007, but would raise a deprecation warning.  Now, "BELL"
+refers to U+1F514, and the name for U+0007 is "ALERT".  All the
+functions in charnames have been correspondingly updated.
+.SS "New Restrictions in Multi-Character Case-Insensitive Matching in Regular Expression Bracketed Character Classes"
+.IX Subsection "New Restrictions in Multi-Character Case-Insensitive Matching in Regular Expression Bracketed Character Classes"
+Unicode has now withdrawn their previous recommendation for regular
+expressions to automatically handle cases where a single character can
+match multiple characters case-insensitively, for example, the letter
+LATIN SMALL LETTER SHARP S and the sequence \f(CW\*(C`ss\*(C'\fR.  This is because
+it turns out to be impracticable to do this correctly in all
+circumstances.  Because Perl has tried to do this as best it can, it
+will continue to do so.  (We are considering an option to turn it off.)
+However, a new restriction is being added on such matches when they
+occur in [bracketed] character classes.  People were specifying
+things such as \f(CW\*(C`/[\e0\-\exff]/i\*(C'\fR, and being surprised that it matches the
+two character sequence \f(CW\*(C`ss\*(C'\fR (since LATIN SMALL LETTER SHARP S occurs in
+this range).  This behavior is also inconsistent with using a
+property instead of a range:  \f(CW\*(C`\ep{Block=Latin1}\*(C'\fR also includes LATIN
+SMALL LETTER SHARP S, but \f(CW\*(C`/[\ep{Block=Latin1}]/i\*(C'\fR does not match \f(CW\*(C`ss\*(C'\fR.
+The new rule is that for there to be a multi-character case-insensitive
+match within a bracketed character class, the character must be
+explicitly listed, and not as an end point of a range.  This more
+closely obeys the Principle of Least Astonishment.  See
+"Bracketed Character Classes" in perlrecharclass.  Note that a bug [perl
+#89774], now fixed as part of this change, prevented the previous
+behavior from working fully.
+.SS "Explicit rules for variable names and identifiers"
+.IX Subsection "Explicit rules for variable names and identifiers"
+Due to an oversight, single character variable names in v5.16 were
+completely unrestricted.  This opened the door to several kinds of
+insanity.  As of v5.18, these now follow the rules of other identifiers,
+in addition to accepting characters that match the \f(CW\*(C`\ep{POSIX_Punct}\*(C'\fR
+property.
+.PP
+There is no longer any difference in the parsing of identifiers
+specified by using braces versus without braces.  For instance, perl
+used to allow \f(CW\*(C`${foo:bar}\*(C'\fR (with a single colon) but not \f(CW$foo:bar\fR.
+Now that both are handled by a single code path, they are both treated
+the same way: both are forbidden.  Note that this change is about the
+range of permissible literal identifiers, not other expressions.
+.SS "Vertical tabs are now whitespace"
+.IX Subsection "Vertical tabs are now whitespace"
+No one could recall why \f(CW\*(C`\es\*(C'\fR didn't match \f(CW\*(C`\ecK\*(C'\fR, the vertical tab.
+Now it does.  Given the extreme rarity of that character, very little
+breakage is expected.  That said, here's what it means:
+.PP
+\&\f(CW\*(C`\es\*(C'\fR in a regex now matches a vertical tab in all circumstances.
+.PP
+Literal vertical tabs in a regex literal are ignored when the \f(CW\*(C`/x\*(C'\fR
+modifier is used.
+.PP
+Leading vertical tabs, alone or mixed with other whitespace, are now
+ignored when interpreting a string as a number.  For example:
+.PP
+.Vb 2
+\&  $dec = " \ecK \et 123";
+\&  $hex = " \ecK \et 0xF";
+\&
+\&  say 0 + $dec;   # was 0 with warning, now 123
+\&  say int $dec;   # was 0, now 123
+\&  say oct $hex;   # was 0, now  15
+.Ve
+.ie n .SS """/(?{})/"" and ""/(??{})/"" have been heavily reworked"
+.el .SS "\f(CW/(?{})/\fP and \f(CW/(??{})/\fP have been heavily reworked"
+.IX Subsection "/(?{})/ and /(??{})/ have been heavily reworked"
+The implementation of this feature has been almost completely rewritten.
+Although its main intent is to fix bugs, some behaviors, especially
+related to the scope of lexical variables, will have changed.  This is
+described more fully in the "Selected Bug Fixes" section.
+.SS "Stricter parsing of substitution replacement"
+.IX Subsection "Stricter parsing of substitution replacement"
+It is no longer possible to abuse the way the parser parses \f(CW\*(C`s///e\*(C'\fR like
+this:
+.PP
+.Vb 3
+\&    %_=(_,"Just another ");
+\&    $_="Perl hacker,\en";
+\&    s//_}\->{_/e;print
+.Ve
+.ie n .SS """given"" now aliases the global $_"
+.el .SS "\f(CWgiven\fP now aliases the global \f(CW$_\fP"
+.IX Subsection "given now aliases the global $_"
+Instead of assigning to an implicit lexical \f(CW$_\fR, \f(CW\*(C`given\*(C'\fR now makes the
+global \f(CW$_\fR an alias for its argument, just like \f(CW\*(C`foreach\*(C'\fR.  However, it
+still uses lexical \f(CW$_\fR if there is lexical \f(CW$_\fR in scope (again, just like
+\&\f(CW\*(C`foreach\*(C'\fR) [perl #114020].
+.SS "The smartmatch family of features are now experimental"
+.IX Subsection "The smartmatch family of features are now experimental"
+Smart match, added in v5.10.0 and significantly revised in v5.10.1, has been
+a regular point of complaint.  Although there are a number of ways in which
+it is useful, it has also proven problematic and confusing for both users and
+implementors of Perl.  There have been a number of proposals on how to best
+address the problem.  It is clear that smartmatch is almost certainly either
+going to change or go away in the future.  Relying on its current behavior
+is not recommended.
+.PP
+Warnings will now be issued when the parser sees \f(CW\*(C`~~\*(C'\fR, \f(CW\*(C`given\*(C'\fR, or \f(CW\*(C`when\*(C'\fR.
+To disable these warnings, you can add this line to the appropriate scope:
+.PP
+.Vb 1
+\&  no if $] >= 5.018, warnings => "experimental::smartmatch";
+.Ve
+.PP
+Consider, though, replacing the use of these features, as they may change
+behavior again before becoming stable.
+.ie n .SS "Lexical $_ is now experimental"
+.el .SS "Lexical \f(CW$_\fP is now experimental"
+.IX Subsection "Lexical $_ is now experimental"
+Since it was introduced in Perl v5.10, it has caused much confusion with no
+obvious solution:
+.IP \(bu 4
+Various modules (e.g., List::Util) expect callback routines to use the
+global \f(CW$_\fR.  \f(CW\*(C`use List::Util \*(Aqfirst\*(Aq; my $_; first { $_ == 1 } @list\*(C'\fR
+does not work as one would expect.
+.IP \(bu 4
+A \f(CW\*(C`my $_\*(C'\fR declaration earlier in the same file can cause confusing closure
+warnings.
+.IP \(bu 4
+The "_" subroutine prototype character allows called subroutines to access
+your lexical \f(CW$_\fR, so it is not really private after all.
+.IP \(bu 4
+Nevertheless, subroutines with a "(@)" prototype and methods cannot access
+the caller's lexical \f(CW$_\fR, unless they are written in XS.
+.IP \(bu 4
+But even XS routines cannot access a lexical \f(CW$_\fR declared, not in the
+calling subroutine, but in an outer scope, iff that subroutine happened not
+to mention \f(CW$_\fR or use any operators that default to \f(CW$_\fR.
+.PP
+It is our hope that lexical \f(CW$_\fR can be rehabilitated, but this may
+cause changes in its behavior.  Please use it with caution until it
+becomes stable.
+.ie n .SS "\fBreadline()\fP with ""$/ = \eN"" now reads N characters, not N bytes"
+.el .SS "\fBreadline()\fP with \f(CW$/ = \eN\fP now reads N characters, not N bytes"
+.IX Subsection "readline() with $/ = N now reads N characters, not N bytes"
+Previously, when reading from a stream with I/O layers such as
+\&\f(CW\*(C`encoding\*(C'\fR, the \fBreadline()\fR function, otherwise known as the \f(CW\*(C`<>\*(C'\fR
+operator, would read \fIN\fR bytes from the top-most layer. [perl #79960]
+.PP
+Now, \fIN\fR characters are read instead.
+.PP
+There is no change in behaviour when reading from streams with no
+extra layers, since bytes map exactly to characters.
+.ie n .SS "Overridden ""glob"" is now passed one argument"
+.el .SS "Overridden \f(CWglob\fP is now passed one argument"
+.IX Subsection "Overridden glob is now passed one argument"
+\&\f(CW\*(C`glob\*(C'\fR overrides used to be passed a magical undocumented second argument
+that identified the caller.  Nothing on CPAN was using this, and it got in
+the way of a bug fix, so it was removed.  If you really need to identify
+the caller, see Devel::Callsite on CPAN.
+.SS "Here doc parsing"
+.IX Subsection "Here doc parsing"
+The body of a here document inside a quote-like operator now always begins
+on the line after the "<<foo" marker.  Previously, it was documented to
+begin on the line following the containing quote-like operator, but that
+was only sometimes the case [perl #114040].
+.SS "Alphanumeric operators must now be separated from the closing delimiter of regular expressions"
+.IX Subsection "Alphanumeric operators must now be separated from the closing delimiter of regular expressions"
+You may no longer write something like:
+.PP
+.Vb 1
+\& m/a/and 1
+.Ve
+.PP
+Instead you must write
+.PP
+.Vb 1
+\& m/a/ and 1
+.Ve
+.PP
+with whitespace separating the operator from the closing delimiter of
+the regular expression.  Not having whitespace has resulted in a
+deprecation warning since Perl v5.14.0.
+.SS "qw(...) can no longer be used as parentheses"
+.IX Subsection "qw(...) can no longer be used as parentheses"
+\&\f(CW\*(C`qw\*(C'\fR lists used to fool the parser into thinking they were always
+surrounded by parentheses.  This permitted some surprising constructions
+such as \f(CW\*(C`foreach $x qw(a b c) {...}\*(C'\fR, which should really be written
+\&\f(CW\*(C`foreach $x (qw(a b c)) {...}\*(C'\fR.  These would sometimes get the lexer into
+the wrong state, so they didn't fully work, and the similar \f(CW\*(C`foreach qw(a
+b c) {...}\*(C'\fR that one might expect to be permitted never worked at all.
+.PP
+This side effect of \f(CW\*(C`qw\*(C'\fR has now been abolished.  It has been deprecated
+since Perl v5.13.11.  It is now necessary to use real parentheses
+everywhere that the grammar calls for them.
+.SS "Interaction of lexical and default warnings"
+.IX Subsection "Interaction of lexical and default warnings"
+Turning on any lexical warnings used first to disable all default warnings
+if lexical warnings were not already enabled:
+.PP
+.Vb 3
+\&    $*; # deprecation warning
+\&    use warnings "void";
+\&    $#; # void warning; no deprecation warning
+.Ve
+.PP
+Now, the \f(CW\*(C`debugging\*(C'\fR, \f(CW\*(C`deprecated\*(C'\fR, \f(CW\*(C`glob\*(C'\fR, \f(CW\*(C`inplace\*(C'\fR and \f(CW\*(C`malloc\*(C'\fR warnings
+categories are left on when turning on lexical warnings (unless they are
+turned off by \f(CW\*(C`no warnings\*(C'\fR, of course).
+.PP
+This may cause deprecation warnings to occur in code that used to be free
+of warnings.
+.PP
+Those are the only categories consisting only of default warnings.  Default
+warnings in other categories are still disabled by \f(CW\*(C`use warnings "category"\*(C'\fR,
+as we do not yet have the infrastructure for controlling
+individual warnings.
+.ie n .SS """state sub"" and ""our sub"""
+.el .SS "\f(CWstate sub\fP and \f(CWour sub\fP"
+.IX Subsection "state sub and our sub"
+Due to an accident of history, \f(CW\*(C`state sub\*(C'\fR and \f(CW\*(C`our sub\*(C'\fR were equivalent
+to a plain \f(CW\*(C`sub\*(C'\fR, so one could even create an anonymous sub with
+\&\f(CW\*(C`our sub { ... }\*(C'\fR.  These are now disallowed outside of the "lexical_subs"
+feature.  Under the "lexical_subs" feature they have new meanings described
+in "Lexical Subroutines" in perlsub.
+.SS "Defined values stored in environment are forced to byte strings"
+.IX Subsection "Defined values stored in environment are forced to byte strings"
+A value stored in an environment variable has always been stringified when
+inherited by child processes.
+.PP
+In this release, when assigning to \f(CW%ENV\fR, values are immediately stringified,
+and converted to be only a byte string.
+.PP
+First, it is forced to be only a string.  Then if the string is utf8 and the
+equivalent of \f(CWutf8::downgrade()\fR works, that result is used; otherwise, the
+equivalent of \f(CWutf8::encode()\fR is used, and a warning is issued about wide
+characters ("Diagnostics").
+.ie n .SS """require"" dies for unreadable files"
+.el .SS "\f(CWrequire\fP dies for unreadable files"
+.IX Subsection "require dies for unreadable files"
+When \f(CW\*(C`require\*(C'\fR encounters an unreadable file, it now dies.  It used to
+ignore the file and continue searching the directories in \f(CW@INC\fR
+[perl #113422].
+.ie n .SS """gv_fetchmeth_*"" and SUPER"
+.el .SS "\f(CWgv_fetchmeth_*\fP and SUPER"
+.IX Subsection "gv_fetchmeth_* and SUPER"
+The various \f(CW\*(C`gv_fetchmeth_*\*(C'\fR XS functions used to treat a package whose
+named ended with \f(CW\*(C`::SUPER\*(C'\fR specially.  A method lookup on the \f(CW\*(C`Foo::SUPER\*(C'\fR
+package would be treated as a \f(CW\*(C`SUPER\*(C'\fR method lookup on the \f(CW\*(C`Foo\*(C'\fR package.  This
+is no longer the case.  To do a \f(CW\*(C`SUPER\*(C'\fR lookup, pass the \f(CW\*(C`Foo\*(C'\fR stash and the
+\&\f(CW\*(C`GV_SUPER\*(C'\fR flag.
+.ie n .SS """split""'s first argument is more consistently interpreted"
+.el .SS "\f(CWsplit\fP's first argument is more consistently interpreted"
+.IX Subsection "split's first argument is more consistently interpreted"
+After some changes earlier in v5.17, \f(CW\*(C`split\*(C'\fR's behavior has been
+simplified: if the PATTERN argument evaluates to a string
+containing one space, it is treated the way that a \fIliteral\fR string
+containing one space once was.
+.SH Deprecations
+.IX Header "Deprecations"
+.SS "Module removals"
+.IX Subsection "Module removals"
+The following modules will be removed from the core distribution in a future
+release, and will at that time need to be installed from CPAN. Distributions
+on CPAN which require these modules will need to list them as prerequisites.
+.PP
+The core versions of these modules will now issue \f(CW"deprecated"\fR\-category
+warnings to alert you to this fact. To silence these deprecation warnings,
+install the modules in question from CPAN.
+.PP
+Note that these are (with rare exceptions) fine modules that you are encouraged
+to continue to use. Their disinclusion from core primarily hinges on their
+necessity to bootstrapping a fully functional, CPAN-capable Perl installation,
+not usually on concerns over their design.
+.IP encoding 4
+.IX Item "encoding"
+The use of this pragma is now strongly discouraged. It conflates the encoding
+of source text with the encoding of I/O data, reinterprets escape sequences in
+source text (a questionable choice), and introduces the UTF\-8 bug to all runtime
+handling of character strings. It is broken as designed and beyond repair.
+.Sp
+For using non-ASCII literal characters in source text, please refer to utf8.
+For dealing with textual I/O data, please refer to Encode and open.
+.IP Archive::Extract 4
+.IX Item "Archive::Extract"
+.PD 0
+.IP B::Lint 4
+.IX Item "B::Lint"
+.IP B::Lint::Debug 4
+.IX Item "B::Lint::Debug"
+.ie n .IP "CPANPLUS and all included ""CPANPLUS::*"" modules" 4
+.el .IP "CPANPLUS and all included \f(CWCPANPLUS::*\fR modules" 4
+.IX Item "CPANPLUS and all included CPANPLUS::* modules"
+.IP Devel::InnerPackage 4
+.IX Item "Devel::InnerPackage"
+.IP Log::Message 4
+.IX Item "Log::Message"
+.IP Log::Message::Config 4
+.IX Item "Log::Message::Config"
+.IP Log::Message::Handlers 4
+.IX Item "Log::Message::Handlers"
+.IP Log::Message::Item 4
+.IX Item "Log::Message::Item"
+.IP Log::Message::Simple 4
+.IX Item "Log::Message::Simple"
+.IP Module::Pluggable 4
+.IX Item "Module::Pluggable"
+.IP Module::Pluggable::Object 4
+.IX Item "Module::Pluggable::Object"
+.IP Object::Accessor 4
+.IX Item "Object::Accessor"
+.IP Pod::LaTeX 4
+.IX Item "Pod::LaTeX"
+.IP Term::UI 4
+.IX Item "Term::UI"
+.IP Term::UI::History 4
+.IX Item "Term::UI::History"
+.PD
+.SS "Deprecated Utilities"
+.IX Subsection "Deprecated Utilities"
+The following utilities will be removed from the core distribution in a
+future release as their associated modules have been deprecated. They
+will remain available with the applicable CPAN distribution.
+.IP cpanp 4
+.IX Item "cpanp"
+.PD 0
+.ie n .IP """cpanp\-run\-perl""" 4
+.el .IP \f(CWcpanp\-run\-perl\fR 4
+.IX Item "cpanp-run-perl"
+.IP cpan2dist 4
+.IX Item "cpan2dist"
+.PD
+These items are part of the \f(CW\*(C`CPANPLUS\*(C'\fR distribution.
+.IP pod2latex 4
+.IX Item "pod2latex"
+This item is part of the \f(CW\*(C`Pod::LaTeX\*(C'\fR distribution.
+.SS PL_sv_objcount
+.IX Subsection "PL_sv_objcount"
+This interpreter-global variable used to track the total number of
+Perl objects in the interpreter. It is no longer maintained and will
+be removed altogether in Perl v5.20.
+.ie n .SS "Five additional characters should be escaped in patterns with ""/x"""
+.el .SS "Five additional characters should be escaped in patterns with \f(CW/x\fP"
+.IX Subsection "Five additional characters should be escaped in patterns with /x"
+When a regular expression pattern is compiled with \f(CW\*(C`/x\*(C'\fR, Perl treats 6
+characters as white space to ignore, such as SPACE and TAB.  However,
+Unicode recommends 11 characters be treated thusly.  We will conform
+with this in a future Perl version.  In the meantime, use of any of the
+missing characters will raise a deprecation warning, unless turned off.
+The five characters are:
+.PP
+.Vb 5
+\&    U+0085 NEXT LINE
+\&    U+200E LEFT\-TO\-RIGHT MARK
+\&    U+200F RIGHT\-TO\-LEFT MARK
+\&    U+2028 LINE SEPARATOR
+\&    U+2029 PARAGRAPH SEPARATOR
+.Ve
+.SS "User-defined charnames with surprising whitespace"
+.IX Subsection "User-defined charnames with surprising whitespace"
+A user-defined character name with trailing or multiple spaces in a row is
+likely a typo.  This now generates a warning when defined, on the assumption
+that uses of it will be unlikely to include the excess whitespace.
+.SS "Various XS-callable functions are now deprecated"
+.IX Subsection "Various XS-callable functions are now deprecated"
+All the functions used to classify characters will be removed from a
+future version of Perl, and should not be used.  With participating C
+compilers (e.g., gcc), compiling any file that uses any of these will
+generate a warning.  These were not intended for public use; there are
+equivalent, faster, macros for most of them.
+.PP
+See "Character classes" in perlapi.  The complete list is:
+.PP
+\&\f(CW\*(C`is_uni_alnum\*(C'\fR, \f(CW\*(C`is_uni_alnumc\*(C'\fR, \f(CW\*(C`is_uni_alnumc_lc\*(C'\fR,
+\&\f(CW\*(C`is_uni_alnum_lc\*(C'\fR, \f(CW\*(C`is_uni_alpha\*(C'\fR, \f(CW\*(C`is_uni_alpha_lc\*(C'\fR,
+\&\f(CW\*(C`is_uni_ascii\*(C'\fR, \f(CW\*(C`is_uni_ascii_lc\*(C'\fR, \f(CW\*(C`is_uni_blank\*(C'\fR,
+\&\f(CW\*(C`is_uni_blank_lc\*(C'\fR, \f(CW\*(C`is_uni_cntrl\*(C'\fR, \f(CW\*(C`is_uni_cntrl_lc\*(C'\fR,
+\&\f(CW\*(C`is_uni_digit\*(C'\fR, \f(CW\*(C`is_uni_digit_lc\*(C'\fR, \f(CW\*(C`is_uni_graph\*(C'\fR,
+\&\f(CW\*(C`is_uni_graph_lc\*(C'\fR, \f(CW\*(C`is_uni_idfirst\*(C'\fR, \f(CW\*(C`is_uni_idfirst_lc\*(C'\fR,
+\&\f(CW\*(C`is_uni_lower\*(C'\fR, \f(CW\*(C`is_uni_lower_lc\*(C'\fR, \f(CW\*(C`is_uni_print\*(C'\fR,
+\&\f(CW\*(C`is_uni_print_lc\*(C'\fR, \f(CW\*(C`is_uni_punct\*(C'\fR, \f(CW\*(C`is_uni_punct_lc\*(C'\fR,
+\&\f(CW\*(C`is_uni_space\*(C'\fR, \f(CW\*(C`is_uni_space_lc\*(C'\fR, \f(CW\*(C`is_uni_upper\*(C'\fR,
+\&\f(CW\*(C`is_uni_upper_lc\*(C'\fR, \f(CW\*(C`is_uni_xdigit\*(C'\fR, \f(CW\*(C`is_uni_xdigit_lc\*(C'\fR,
+\&\f(CW\*(C`is_utf8_alnum\*(C'\fR, \f(CW\*(C`is_utf8_alnumc\*(C'\fR, \f(CW\*(C`is_utf8_alpha\*(C'\fR,
+\&\f(CW\*(C`is_utf8_ascii\*(C'\fR, \f(CW\*(C`is_utf8_blank\*(C'\fR, \f(CW\*(C`is_utf8_char\*(C'\fR,
+\&\f(CW\*(C`is_utf8_cntrl\*(C'\fR, \f(CW\*(C`is_utf8_digit\*(C'\fR, \f(CW\*(C`is_utf8_graph\*(C'\fR,
+\&\f(CW\*(C`is_utf8_idcont\*(C'\fR, \f(CW\*(C`is_utf8_idfirst\*(C'\fR, \f(CW\*(C`is_utf8_lower\*(C'\fR,
+\&\f(CW\*(C`is_utf8_mark\*(C'\fR, \f(CW\*(C`is_utf8_perl_space\*(C'\fR, \f(CW\*(C`is_utf8_perl_word\*(C'\fR,
+\&\f(CW\*(C`is_utf8_posix_digit\*(C'\fR, \f(CW\*(C`is_utf8_print\*(C'\fR, \f(CW\*(C`is_utf8_punct\*(C'\fR,
+\&\f(CW\*(C`is_utf8_space\*(C'\fR, \f(CW\*(C`is_utf8_upper\*(C'\fR, \f(CW\*(C`is_utf8_xdigit\*(C'\fR,
+\&\f(CW\*(C`is_utf8_xidcont\*(C'\fR, \f(CW\*(C`is_utf8_xidfirst\*(C'\fR.
+.PP
+In addition these three functions that have never worked properly are
+deprecated:
+\&\f(CW\*(C`to_uni_lower_lc\*(C'\fR, \f(CW\*(C`to_uni_title_lc\*(C'\fR, and \f(CW\*(C`to_uni_upper_lc\*(C'\fR.
+.SS "Certain rare uses of backslashes within regexes are now deprecated"
+.IX Subsection "Certain rare uses of backslashes within regexes are now deprecated"
+There are three pairs of characters that Perl recognizes as
+metacharacters in regular expression patterns: \f(CW\*(C`{}\*(C'\fR, \f(CW\*(C`[]\*(C'\fR, and \f(CW\*(C`()\*(C'\fR.
+These can be used as well to delimit patterns, as in:
+.PP
+.Vb 2
+\&  m{foo}
+\&  s(foo)(bar)
+.Ve
+.PP
+Since they are metacharacters, they have special meaning to regular
+expression patterns, and it turns out that you can't turn off that
+special meaning by the normal means of preceding them with a backslash,
+if you use them, paired, within a pattern delimited by them.  For
+example, in
+.PP
+.Vb 1
+\&  m{foo\e{1,3\e}}
+.Ve
+.PP
+the backslashes do not change the behavior, and this matches
+\&\f(CW"f\ o"\fR followed by one to three more occurrences of \f(CW"o"\fR.
+.PP
+Usages like this, where they are interpreted as metacharacters, are
+exceedingly rare; we think there are none, for example, in all of CPAN.
+Hence, this deprecation should affect very little code.  It does give
+notice, however, that any such code needs to change, which will in turn
+allow us to change the behavior in future Perl versions so that the
+backslashes do have an effect, and without fear that we are silently
+breaking any existing code.
+.ie n .SS "Splitting the tokens ""(?"" and ""(*"" in regular expressions"
+.el .SS "Splitting the tokens \f(CW(?\fP and \f(CW(*\fP in regular expressions"
+.IX Subsection "Splitting the tokens (? and (* in regular expressions"
+A deprecation warning is now raised if the \f(CW\*(C`(\*(C'\fR and \f(CW\*(C`?\*(C'\fR are separated
+by white space or comments in \f(CW\*(C`(?...)\*(C'\fR regular expression constructs.
+Similarly, if the \f(CW\*(C`(\*(C'\fR and \f(CW\*(C`*\*(C'\fR are separated in \f(CW\*(C`(*VERB...)\*(C'\fR
+constructs.
+.SS "Pre-PerlIO IO implementations"
+.IX Subsection "Pre-PerlIO IO implementations"
+In theory, you can currently build perl without PerlIO.  Instead, you'd use a
+wrapper around stdio or sfio.  In practice, this isn't very useful.  It's not
+well tested, and without any support for IO layers or (thus) Unicode, it's not
+much of a perl.  Building without PerlIO will most likely be removed in the
+next version of perl.
+.PP
+PerlIO supports a \f(CW\*(C`stdio\*(C'\fR layer if stdio use is desired.  Similarly a
+sfio layer could be produced in the future, if needed.
+.SH "Future Deprecations"
+.IX Header "Future Deprecations"
+.IP \(bu 4
+Platforms without support infrastructure
+.Sp
+Both Windows CE and z/OS have been historically under-maintained, and are
+currently neither successfully building nor regularly being smoke tested.
+Efforts are underway to change this situation, but it should not be taken for
+granted that the platforms are safe and supported.  If they do not become
+buildable and regularly smoked, support for them may be actively removed in
+future releases.  If you have an interest in these platforms and you can lend
+your time, expertise, or hardware to help support these platforms, please let
+the perl development effort know by emailing \f(CW\*(C`perl5\-porters@perl.org\*(C'\fR.
+.Sp
+Some platforms that appear otherwise entirely dead are also on the short list
+for removal between now and v5.20.0:
+.RS 4
+.IP DG/UX 4
+.IX Item "DG/UX"
+.PD 0
+.IP NeXT 4
+.IX Item "NeXT"
+.RE
+.RS 4
+.PD
+.Sp
+We also think it likely that current versions of Perl will no longer
+build AmigaOS, DJGPP, NetWare (natively), OS/2 and Plan 9. If you
+are using Perl on such a platform and have an interest in ensuring
+Perl's future on them, please contact us.
+.Sp
+We believe that Perl has long been unable to build on mixed endian
+architectures (such as PDP\-11s), and intend to remove any remaining
+support code. Similarly, code supporting the long unmaintained GNU
+dld will be removed soon if no-one makes themselves known as an
+active user.
+.RE
+.IP \(bu 4
+Swapping of $< and $>
+.Sp
+Perl has supported the idiom of swapping $< and $> (and likewise $( and
+$)) to temporarily drop permissions since 5.0, like this:
+.Sp
+.Vb 1
+\&    ($<, $>) = ($>, $<);
+.Ve
+.Sp
+However, this idiom modifies the real user/group id, which can have
+undesirable side-effects, is no longer useful on any platform perl
+supports and complicates the implementation of these variables and list
+assignment in general.
+.Sp
+As an alternative, assignment only to \f(CW$>\fR is recommended:
+.Sp
+.Vb 1
+\&    local $> = $<;
+.Ve
+.Sp
+See also: Setuid Demystified <http://www.cs.berkeley.edu/~daw/papers/setuid-usenix02.pdf>.
+.IP \(bu 4
+\&\f(CW\*(C`microperl\*(C'\fR, long broken and of unclear present purpose, will be removed.
+.IP \(bu 4
+Revamping \f(CW"\eQ"\fR semantics in double-quotish strings when combined with
+other escapes.
+.Sp
+There are several bugs and inconsistencies involving combinations
+of \f(CW\*(C`\eQ\*(C'\fR and escapes like \f(CW\*(C`\ex\*(C'\fR, \f(CW\*(C`\eL\*(C'\fR, etc., within a \f(CW\*(C`\eQ...\eE\*(C'\fR pair.
+These need to be fixed, and doing so will necessarily change current
+behavior.  The changes have not yet been settled.
+.IP \(bu 4
+Use of \f(CW$x\fR, where \f(CW\*(C`x\*(C'\fR stands for any actual (non-printing) C0 control
+character will be disallowed in a future Perl version.  Use \f(CW\*(C`${x}\*(C'\fR
+instead (where again \f(CW\*(C`x\*(C'\fR stands for a control character),
+or better, \f(CW$^A\fR , where \f(CW\*(C`^\*(C'\fR is a caret (CIRCUMFLEX ACCENT),
+and \f(CW\*(C`A\*(C'\fR stands for any of the characters listed at the end of
+"OPERATOR DIFFERENCES" in perlebcdic.
+.SH "Performance Enhancements"
+.IX Header "Performance Enhancements"
+.IP \(bu 4
+Lists of lexical variable declarations (\f(CW\*(C`my($x, $y)\*(C'\fR) are now optimised
+down to a single op and are hence faster than before.
+.IP \(bu 4
+A new C preprocessor define \f(CW\*(C`NO_TAINT_SUPPORT\*(C'\fR was added that, if set,
+disables Perl's taint support altogether.  Using the \-T or \-t command
+line flags will cause a fatal error.  Beware that both core tests as
+well as many a CPAN distribution's tests will fail with this change.  On
+the upside, it provides a small performance benefit due to reduced
+branching.
+.Sp
+\&\fBDo not enable this unless you know exactly what you are getting yourself
+into.\fR
+.IP \(bu 4
+\&\f(CW\*(C`pack\*(C'\fR with constant arguments is now constant folded in most cases
+[perl #113470].
+.IP \(bu 4
+Speed up in regular expression matching against Unicode properties.  The
+largest gain is for \f(CW\*(C`\eX\*(C'\fR, the Unicode "extended grapheme cluster."  The
+gain for it is about 35% \- 40%.  Bracketed character classes, e.g.,
+\&\f(CW\*(C`[0\-9\ex{100}]\*(C'\fR containing code points above 255 are also now faster.
+.IP \(bu 4
+On platforms supporting it, several former macros are now implemented as static
+inline functions. This should speed things up slightly on non-GCC platforms.
+.IP \(bu 4
+The optimisation of hashes in boolean context has been extended to
+affect \f(CWscalar(%hash)\fR, \f(CW\*(C`%hash ? ... : ...\*(C'\fR, and \f(CW\*(C`sub { %hash || ... }\*(C'\fR.
+.IP \(bu 4
+Filetest operators manage the stack in a fractionally more efficient manner.
+.IP \(bu 4
+Globs used in a numeric context are now numified directly in most cases,
+rather than being numified via stringification.
+.IP \(bu 4
+The \f(CW\*(C`x\*(C'\fR repetition operator is now folded to a single constant at compile
+time if called in scalar context with constant operands and no parentheses
+around the left operand.
+.SH "Modules and Pragmata"
+.IX Header "Modules and Pragmata"
+.SS "New Modules and Pragmata"
+.IX Subsection "New Modules and Pragmata"
+.IP \(bu 4
+Config::Perl::V version 0.16 has been added as a dual-lifed module.
+It provides structured data retrieval of \f(CW\*(C`perl \-V\*(C'\fR output including
+information only known to the \f(CW\*(C`perl\*(C'\fR binary and not available via Config.
+.SS "Updated Modules and Pragmata"
+.IX Subsection "Updated Modules and Pragmata"
+For a complete list of updates, run:
+.PP
+.Vb 1
+\&  $ corelist \-\-diff 5.16.0 5.18.0
+.Ve
+.PP
+You can substitute your favorite version in place of \f(CW5.16.0\fR, too.
+.IP \(bu 4
+Archive::Extract has been upgraded to 0.68.
+.Sp
+Work around an edge case on Linux with Busybox's unzip.
+.IP \(bu 4
+Archive::Tar has been upgraded to 1.90.
+.Sp
+ptar now supports the \-T option as well as dashless options
+[rt.cpan.org #75473], [rt.cpan.org #75475].
+.Sp
+Auto-encode filenames marked as UTF\-8 [rt.cpan.org #75474].
+.Sp
+Don't use \f(CW\*(C`tell\*(C'\fR on IO::Zlib handles [rt.cpan.org #64339].
+.Sp
+Don't try to \f(CW\*(C`chown\*(C'\fR on symlinks.
+.IP \(bu 4
+autodie has been upgraded to 2.13.
+.Sp
+\&\f(CW\*(C`autodie\*(C'\fR now plays nicely with the 'open' pragma.
+.IP \(bu 4
+B has been upgraded to 1.42.
+.Sp
+The \f(CW\*(C`stashoff\*(C'\fR method of COPs has been added.   This provides access to an
+internal field added in perl 5.16 under threaded builds [perl #113034].
+.Sp
+\&\f(CW\*(C`B::COP::stashpv\*(C'\fR now supports UTF\-8 package names and embedded NULs.
+.Sp
+All \f(CW\*(C`CVf_*\*(C'\fR and \f(CW\*(C`GVf_*\*(C'\fR
+and more SV-related flag values are now provided as constants in the \f(CW\*(C`B::\*(C'\fR
+namespace and available for export.  The default export list has not changed.
+.Sp
+This makes the module work with the new pad API.
+.IP \(bu 4
+B::Concise has been upgraded to 0.95.
+.Sp
+The \f(CW\*(C`\-nobanner\*(C'\fR option has been fixed, and \f(CW\*(C`format\*(C'\fRs can now be dumped.
+When passed a sub name to dump, it will check also to see whether it
+is the name of a format.  If a sub and a format share the same name,
+it will dump both.
+.Sp
+This adds support for the new \f(CW\*(C`OpMAYBE_TRUEBOOL\*(C'\fR and \f(CW\*(C`OPpTRUEBOOL\*(C'\fR flags.
+.IP \(bu 4
+B::Debug has been upgraded to 1.18.
+.Sp
+This adds support (experimentally) for \f(CW\*(C`B::PADLIST\*(C'\fR, which was
+added in Perl 5.17.4.
+.IP \(bu 4
+B::Deparse has been upgraded to 1.20.
+.Sp
+Avoid warning when run under \f(CW\*(C`perl \-w\*(C'\fR.
+.Sp
+It now deparses
+loop controls with the correct precedence, and multiple statements in a
+\&\f(CW\*(C`format\*(C'\fR line are also now deparsed correctly.
+.Sp
+This release suppresses trailing semicolons in formats.
+.Sp
+This release adds stub deparsing for lexical subroutines.
+.Sp
+It no longer dies when deparsing \f(CW\*(C`sort\*(C'\fR without arguments.  It now
+correctly omits the comma for \f(CW\*(C`system $prog @args\*(C'\fR and \f(CWexec $prog
+@args\fR.
+.IP \(bu 4
+bignum, bigint and bigrat have been upgraded to 0.33.
+.Sp
+The overrides for \f(CW\*(C`hex\*(C'\fR and \f(CW\*(C`oct\*(C'\fR have been rewritten, eliminating
+several problems, and making one incompatible change:
+.RS 4
+.IP \(bu 4
+Formerly, whichever of \f(CW\*(C`use bigint\*(C'\fR or \f(CW\*(C`use bigrat\*(C'\fR was compiled later
+would take precedence over the other, causing \f(CW\*(C`hex\*(C'\fR and \f(CW\*(C`oct\*(C'\fR not to
+respect the other pragma when in scope.
+.IP \(bu 4
+Using any of these three pragmata would cause \f(CW\*(C`hex\*(C'\fR and \f(CW\*(C`oct\*(C'\fR anywhere
+else in the program to evaluate their arguments in list context and prevent
+them from inferring \f(CW$_\fR when called without arguments.
+.IP \(bu 4
+Using any of these three pragmata would make \f(CWoct("1234")\fR return 1234
+(for any number not beginning with 0) anywhere in the program.  Now "1234"
+is translated from octal to decimal, whether within the pragma's scope or
+not.
+.IP \(bu 4
+The global overrides that facilitate lexical use of \f(CW\*(C`hex\*(C'\fR and \f(CW\*(C`oct\*(C'\fR now
+respect any existing overrides that were in place before the new overrides
+were installed, falling back to them outside of the scope of \f(CW\*(C`use bignum\*(C'\fR.
+.IP \(bu 4
+\&\f(CW\*(C`use bignum "hex"\*(C'\fR, \f(CW\*(C`use bignum "oct"\*(C'\fR and similar invocations for bigint
+and bigrat now export a \f(CW\*(C`hex\*(C'\fR or \f(CW\*(C`oct\*(C'\fR function, instead of providing a
+global override.
+.RE
+.RS 4
+.RE
+.IP \(bu 4
+Carp has been upgraded to 1.29.
+.Sp
+Carp is no longer confused when \f(CW\*(C`caller\*(C'\fR returns undef for a package that
+has been deleted.
+.Sp
+The \f(CWlongmess()\fR and \f(CWshortmess()\fR functions are now documented.
+.IP \(bu 4
+CGI has been upgraded to 3.63.
+.Sp
+Unrecognized HTML escape sequences are now handled better, problematic
+trailing newlines are no longer inserted after <form> tags
+by \f(CWstartform()\fR or \f(CWstart_form()\fR, and bogus "Insecure Dependency"
+warnings appearing with some versions of perl are now worked around.
+.IP \(bu 4
+Class::Struct has been upgraded to 0.64.
+.Sp
+The constructor now respects overridden accessor methods [perl #29230].
+.IP \(bu 4
+Compress::Raw::Bzip2 has been upgraded to 2.060.
+.Sp
+The misuse of Perl's "magic" API has been fixed.
+.IP \(bu 4
+Compress::Raw::Zlib has been upgraded to 2.060.
+.Sp
+Upgrade bundled zlib to version 1.2.7.
+.Sp
+Fix build failures on Irix, Solaris, and Win32, and also when building as C++
+[rt.cpan.org #69985], [rt.cpan.org #77030], [rt.cpan.org #75222].
+.Sp
+The misuse of Perl's "magic" API has been fixed.
+.Sp
+\&\f(CWcompress()\fR, \f(CWuncompress()\fR, \f(CWmemGzip()\fR and \f(CWmemGunzip()\fR have
+been speeded up by making parameter validation more efficient.
+.IP \(bu 4
+CPAN::Meta::Requirements has been upgraded to 2.122.
+.Sp
+Treat undef requirements to \f(CW\*(C`from_string_hash\*(C'\fR as 0 (with a warning).
+.Sp
+Added \f(CW\*(C`requirements_for_module\*(C'\fR method.
+.IP \(bu 4
+CPANPLUS has been upgraded to 0.9135.
+.Sp
+Allow adding \fIblib/script\fR to PATH.
+.Sp
+Save the history between invocations of the shell.
+.Sp
+Handle multiple \f(CW\*(C`makemakerargs\*(C'\fR and \f(CW\*(C`makeflags\*(C'\fR arguments better.
+.Sp
+This resolves issues with the SQLite source engine.
+.IP \(bu 4
+Data::Dumper has been upgraded to 2.145.
+.Sp
+It has been optimized to only build a seen-scalar hash as necessary,
+thereby speeding up serialization drastically.
+.Sp
+Additional tests were added in order to improve statement, branch, condition
+and subroutine coverage.  On the basis of the coverage analysis, some of the
+internals of Dumper.pm were refactored.  Almost all methods are now
+documented.
+.IP \(bu 4
+DB_File has been upgraded to 1.827.
+.Sp
+The main Perl module no longer uses the \f(CW"@_"\fR construct.
+.IP \(bu 4
+Devel::Peek has been upgraded to 1.11.
+.Sp
+This fixes compilation with C++ compilers and makes the module work with
+the new pad API.
+.IP \(bu 4
+Digest::MD5 has been upgraded to 2.52.
+.Sp
+Fix \f(CW\*(C`Digest::Perl::MD5\*(C'\fR OO fallback [rt.cpan.org #66634].
+.IP \(bu 4
+Digest::SHA has been upgraded to 5.84.
+.Sp
+This fixes a double-free bug, which might have caused vulnerabilities
+in some cases.
+.IP \(bu 4
+DynaLoader has been upgraded to 1.18.
+.Sp
+This is due to a minor code change in the XS for the VMS implementation.
+.Sp
+This fixes warnings about using \f(CW\*(C`CODE\*(C'\fR sections without an \f(CW\*(C`OUTPUT\*(C'\fR
+section.
+.IP \(bu 4
+Encode has been upgraded to 2.49.
+.Sp
+The Mac alias x\-mac-ce has been added, and various bugs have been fixed
+in Encode::Unicode, Encode::UTF7 and Encode::GSM0338.
+.IP \(bu 4
+Env has been upgraded to 1.04.
+.Sp
+Its SPLICE implementation no longer misbehaves in list context.
+.IP \(bu 4
+ExtUtils::CBuilder has been upgraded to 0.280210.
+.Sp
+Manifest files are now correctly embedded for those versions of VC++ which
+make use of them. [perl #111782, #111798].
+.Sp
+A list of symbols to export can now be passed to \f(CWlink()\fR when on
+Windows, as on other OSes [perl #115100].
+.IP \(bu 4
+ExtUtils::ParseXS has been upgraded to 3.18.
+.Sp
+The generated C code now avoids unnecessarily incrementing
+\&\f(CW\*(C`PL_amagic_generation\*(C'\fR on Perl versions where it's done automatically
+(or on current Perl where the variable no longer exists).
+.Sp
+This avoids a bogus warning for initialised XSUB non-parameters [perl
+#112776].
+.IP \(bu 4
+File::Copy has been upgraded to 2.26.
+.Sp
+\&\f(CWcopy()\fR no longer zeros files when copying into the same directory,
+and also now fails (as it has long been documented to do) when attempting
+to copy a file over itself.
+.IP \(bu 4
+File::DosGlob has been upgraded to 1.10.
+.Sp
+The internal cache of file names that it keeps for each caller is now
+freed when that caller is freed.  This means
+\&\f(CW\*(C`use File::DosGlob \*(Aqglob\*(Aq; eval \*(Aqscalar <*>\*(Aq\*(C'\fR no longer leaks memory.
+.IP \(bu 4
+File::Fetch has been upgraded to 0.38.
+.Sp
+Added the 'file_default' option for URLs that do not have a file
+component.
+.Sp
+Use \f(CW\*(C`File::HomeDir\*(C'\fR when available, and provide \f(CW\*(C`PERL5_CPANPLUS_HOME\*(C'\fR to
+override the autodetection.
+.Sp
+Always re-fetch \fICHECKSUMS\fR if \f(CW\*(C`fetchdir\*(C'\fR is set.
+.IP \(bu 4
+File::Find has been upgraded to 1.23.
+.Sp
+This fixes inconsistent unixy path handling on VMS.
+.Sp
+Individual files may now appear in list of directories to be searched
+[perl #59750].
+.IP \(bu 4
+File::Glob has been upgraded to 1.20.
+.Sp
+File::Glob has had exactly the same fix as File::DosGlob.  Since it is
+what Perl's own \f(CW\*(C`glob\*(C'\fR operator itself uses (except on VMS), this means
+\&\f(CW\*(C`eval \*(Aqscalar <*>\*(Aq\*(C'\fR no longer leaks.
+.Sp
+A space-separated list of patterns return long lists of results no longer
+results in memory corruption or crashes.  This bug was introduced in
+Perl 5.16.0.  [perl #114984]
+.IP \(bu 4
+File::Spec::Unix has been upgraded to 3.40.
+.Sp
+\&\f(CW\*(C`abs2rel\*(C'\fR could produce incorrect results when given two relative paths or
+the root directory twice [perl #111510].
+.IP \(bu 4
+File::stat has been upgraded to 1.07.
+.Sp
+\&\f(CW\*(C`File::stat\*(C'\fR ignores the filetest pragma, and warns when used in
+combination therewith.  But it was not warning for \f(CW\*(C`\-r\*(C'\fR.  This has been
+fixed [perl #111640].
+.Sp
+\&\f(CW\*(C`\-p\*(C'\fR now works, and does not return false for pipes [perl #111638].
+.Sp
+Previously \f(CW\*(C`File::stat\*(C'\fR's overloaded \f(CW\*(C`\-x\*(C'\fR and \f(CW\*(C`\-X\*(C'\fR operators did not give
+the correct results for directories or executable files when running as
+root. They had been treating executable permissions for root just like for
+any other user, performing group membership tests \fIetc\fR for files not owned
+by root. They now follow the correct Unix behaviour \- for a directory they
+are always true, and for a file if any of the three execute permission bits
+are set then they report that root can execute the file. Perl's builtin
+\&\f(CW\*(C`\-x\*(C'\fR and \f(CW\*(C`\-X\*(C'\fR operators have always been correct.
+.IP \(bu 4
+File::Temp has been upgraded to 0.23
+.Sp
+Fixes various bugs involving directory removal.  Defers unlinking tempfiles if
+the initial unlink fails, which fixes problems on NFS.
+.IP \(bu 4
+GDBM_File has been upgraded to 1.15.
+.Sp
+The undocumented optional fifth parameter to \f(CW\*(C`TIEHASH\*(C'\fR has been
+removed. This was intended to provide control of the callback used by
+\&\f(CW\*(C`gdbm*\*(C'\fR functions in case of fatal errors (such as filesystem problems),
+but did not work (and could never have worked). No code on CPAN even
+attempted to use it. The callback is now always the previous default,
+\&\f(CW\*(C`croak\*(C'\fR. Problems on some platforms with how the \f(CW\*(C`C\*(C'\fR \f(CW\*(C`croak\*(C'\fR function
+is called have also been resolved.
+.IP \(bu 4
+Hash::Util has been upgraded to 0.15.
+.Sp
+\&\f(CW\*(C`hash_unlocked\*(C'\fR and \f(CW\*(C`hashref_unlocked\*(C'\fR now returns true if the hash is
+unlocked, instead of always returning false [perl #112126].
+.Sp
+\&\f(CW\*(C`hash_unlocked\*(C'\fR, \f(CW\*(C`hashref_unlocked\*(C'\fR, \f(CW\*(C`lock_hash_recurse\*(C'\fR and
+\&\f(CW\*(C`unlock_hash_recurse\*(C'\fR are now exportable [perl #112126].
+.Sp
+Two new functions, \f(CW\*(C`hash_locked\*(C'\fR and \f(CW\*(C`hashref_locked\*(C'\fR, have been added.
+Oddly enough, these two functions were already exported, even though they
+did not exist [perl #112126].
+.IP \(bu 4
+HTTP::Tiny has been upgraded to 0.025.
+.Sp
+Add SSL verification features [github #6], [github #9].
+.Sp
+Include the final URL in the response hashref.
+.Sp
+Add \f(CW\*(C`local_address\*(C'\fR option.
+.Sp
+This improves SSL support.
+.IP \(bu 4
+IO has been upgraded to 1.28.
+.Sp
+\&\f(CWsync()\fR can now be called on read-only file handles [perl #64772].
+.Sp
+IO::Socket tries harder to cache or otherwise fetch socket
+information.
+.IP \(bu 4
+IPC::Cmd has been upgraded to 0.80.
+.Sp
+Use \f(CW\*(C`POSIX::_exit\*(C'\fR instead of \f(CW\*(C`exit\*(C'\fR in \f(CW\*(C`run_forked\*(C'\fR [rt.cpan.org #76901].
+.IP \(bu 4
+IPC::Open3 has been upgraded to 1.13.
+.Sp
+The \f(CWopen3()\fR function no longer uses \f(CWPOSIX::close()\fR to close file
+descriptors since that breaks the ref-counting of file descriptors done by
+PerlIO in cases where the file descriptors are shared by PerlIO streams,
+leading to attempts to close the file descriptors a second time when
+any such PerlIO streams are closed later on.
+.IP \(bu 4
+Locale::Codes has been upgraded to 3.25.
+.Sp
+It includes some new codes.
+.IP \(bu 4
+Memoize has been upgraded to 1.03.
+.Sp
+Fix the \f(CW\*(C`MERGE\*(C'\fR cache option.
+.IP \(bu 4
+Module::Build has been upgraded to 0.4003.
+.Sp
+Fixed bug where modules without \f(CW$VERSION\fR might have a version of '0' listed
+in 'provides' metadata, which will be rejected by PAUSE.
+.Sp
+Fixed bug in PodParser to allow numerals in module names.
+.Sp
+Fixed bug where giving arguments twice led to them becoming arrays, resulting
+in install paths like \fR\f(BIARRAY\fR\fI\|(0xdeadbeef)/lib/Foo.pm\fR.
+.Sp
+A minor bug fix allows markup to be used around the leading "Name" in
+a POD "abstract" line, and some documentation improvements have been made.
+.IP \(bu 4
+Module::CoreList has been upgraded to 2.90
+.Sp
+Version information is now stored as a delta, which greatly reduces the
+size of the \fICoreList.pm\fR file.
+.Sp
+This restores compatibility with older versions of perl and cleans up
+the corelist data for various modules.
+.IP \(bu 4
+Module::Load::Conditional has been upgraded to 0.54.
+.Sp
+Fix use of \f(CW\*(C`requires\*(C'\fR on perls installed to a path with spaces.
+.Sp
+Various enhancements include the new use of Module::Metadata.
+.IP \(bu 4
+Module::Metadata has been upgraded to 1.000011.
+.Sp
+The creation of a Module::Metadata object for a typical module file has
+been sped up by about 40%, and some spurious warnings about \f(CW$VERSION\fRs
+have been suppressed.
+.IP \(bu 4
+Module::Pluggable has been upgraded to 4.7.
+.Sp
+Amongst other changes, triggers are now allowed on events, which gives
+a powerful way to modify behaviour.
+.IP \(bu 4
+Net::Ping has been upgraded to 2.41.
+.Sp
+This fixes some test failures on Windows.
+.IP \(bu 4
+Opcode has been upgraded to 1.25.
+.Sp
+Reflect the removal of the boolkeys opcode and the addition of the
+clonecv, introcv and padcv opcodes.
+.IP \(bu 4
+overload has been upgraded to 1.22.
+.Sp
+\&\f(CW\*(C`no overload\*(C'\fR now warns for invalid arguments, just like \f(CW\*(C`use overload\*(C'\fR.
+.IP \(bu 4
+PerlIO::encoding has been upgraded to 0.16.
+.Sp
+This is the module implementing the ":encoding(...)" I/O layer.  It no
+longer corrupts memory or crashes when the encoding back-end reallocates
+the buffer or gives it a typeglob or shared hash key scalar.
+.IP \(bu 4
+PerlIO::scalar has been upgraded to 0.16.
+.Sp
+The buffer scalar supplied may now only contain code points 0xFF or
+lower. [perl #109828]
+.IP \(bu 4
+Perl::OSType has been upgraded to 1.003.
+.Sp
+This fixes a bug detecting the VOS operating system.
+.IP \(bu 4
+Pod::Html has been upgraded to 1.18.
+.Sp
+The option \f(CW\*(C`\-\-libpods\*(C'\fR has been reinstated. It is deprecated, and its use
+does nothing other than issue a warning that it is no longer supported.
+.Sp
+Since the HTML files generated by pod2html claim to have a UTF\-8 charset,
+actually write the files out using UTF\-8 [perl #111446].
+.IP \(bu 4
+Pod::Simple has been upgraded to 3.28.
+.Sp
+Numerous improvements have been made, mostly to Pod::Simple::XHTML,
+which also has a compatibility change: the \f(CW\*(C`codes_in_verbatim\*(C'\fR option
+is now disabled by default.  See \fIcpan/Pod\-Simple/ChangeLog\fR for the
+full details.
+.IP \(bu 4
+re has been upgraded to 0.23
+.Sp
+Single character [class]es like \f(CW\*(C`/[s]/\*(C'\fR or \f(CW\*(C`/[s]/i\*(C'\fR are now optimized
+as if they did not have the brackets, i.e. \f(CW\*(C`/s/\*(C'\fR or \f(CW\*(C`/s/i\*(C'\fR.
+.Sp
+See note about \f(CW\*(C`op_comp\*(C'\fR in the "Internal Changes" section below.
+.IP \(bu 4
+Safe has been upgraded to 2.35.
+.Sp
+Fix interactions with \f(CW\*(C`Devel::Cover\*(C'\fR.
+.Sp
+Don't eval code under \f(CW\*(C`no strict\*(C'\fR.
+.IP \(bu 4
+Scalar::Util has been upgraded to version 1.27.
+.Sp
+Fix an overloading issue with \f(CW\*(C`sum\*(C'\fR.
+.Sp
+\&\f(CW\*(C`first\*(C'\fR and \f(CW\*(C`reduce\*(C'\fR now check the callback first (so \f(CW&first(1)\fR is
+disallowed).
+.Sp
+Fix \f(CW\*(C`tainted\*(C'\fR on magical values [rt.cpan.org #55763].
+.Sp
+Fix \f(CW\*(C`sum\*(C'\fR on previously magical values [rt.cpan.org #61118].
+.Sp
+Fix reading past the end of a fixed buffer [rt.cpan.org #72700].
+.IP \(bu 4
+Search::Dict has been upgraded to 1.07.
+.Sp
+No longer require \f(CW\*(C`stat\*(C'\fR on filehandles.
+.Sp
+Use \f(CW\*(C`fc\*(C'\fR for casefolding.
+.IP \(bu 4
+Socket has been upgraded to 2.009.
+.Sp
+Constants and functions required for IP multicast source group membership
+have been added.
+.Sp
+\&\f(CWunpack_sockaddr_in()\fR and \f(CWunpack_sockaddr_in6()\fR now return just the IP
+address in scalar context, and \f(CWinet_ntop()\fR now guards against incorrect
+length scalars being passed in.
+.Sp
+This fixes an uninitialized memory read.
+.IP \(bu 4
+Storable has been upgraded to 2.41.
+.Sp
+Modifying \f(CW$_[0]\fR within \f(CW\*(C`STORABLE_freeze\*(C'\fR no longer results in crashes
+[perl #112358].
+.Sp
+An object whose class implements \f(CW\*(C`STORABLE_attach\*(C'\fR is now thawed only once
+when there are multiple references to it in the structure being thawed
+[perl #111918].
+.Sp
+Restricted hashes were not always thawed correctly [perl #73972].
+.Sp
+Storable would croak when freezing a blessed REF object with a
+\&\f(CWSTORABLE_freeze()\fR method [perl #113880].
+.Sp
+It can now freeze and thaw vstrings correctly.  This causes a slight
+incompatible change in the storage format, so the format version has
+increased to 2.9.
+.Sp
+This contains various bugfixes, including compatibility fixes for older
+versions of Perl and vstring handling.
+.IP \(bu 4
+Sys::Syslog has been upgraded to 0.32.
+.Sp
+This contains several bug fixes relating to \f(CWgetservbyname()\fR,
+\&\f(CWsetlogsock()\fRand log levels in \f(CWsyslog()\fR, together with fixes for
+Windows, Haiku-OS and GNU/kFreeBSD.  See \fIcpan/Sys\-Syslog/Changes\fR
+for the full details.
+.IP \(bu 4
+Term::ANSIColor has been upgraded to 4.02.
+.Sp
+Add support for italics.
+.Sp
+Improve error handling.
+.IP \(bu 4
+Term::ReadLine has been upgraded to 1.10.  This fixes the
+use of the \fBcpan\fR and \fBcpanp\fR shells on Windows in the event that the current
+drive happens to contain a \fI\edev\etty\fR file.
+.IP \(bu 4
+Test::Harness has been upgraded to 3.26.
+.Sp
+Fix glob semantics on Win32 [rt.cpan.org #49732].
+.Sp
+Don't use \f(CW\*(C`Win32::GetShortPathName\*(C'\fR when calling perl [rt.cpan.org #47890].
+.Sp
+Ignore \-T when reading shebang [rt.cpan.org #64404].
+.Sp
+Handle the case where we don't know the wait status of the test more
+gracefully.
+.Sp
+Make the test summary 'ok' line overridable so that it can be changed to a
+plugin to make the output of prove idempotent.
+.Sp
+Don't run world-writable files.
+.IP \(bu 4
+Text::Tabs and Text::Wrap have been upgraded to
+2012.0818.  Support for Unicode combining characters has been added to them
+both.
+.IP \(bu 4
+threads::shared has been upgraded to 1.31.
+.Sp
+This adds the option to warn about or ignore attempts to clone structures
+that can't be cloned, as opposed to just unconditionally dying in
+that case.
+.Sp
+This adds support for dual-valued values as created by
+Scalar::Util::dualvar.
+.IP \(bu 4
+Tie::StdHandle has been upgraded to 4.3.
+.Sp
+\&\f(CW\*(C`READ\*(C'\fR now respects the offset argument to \f(CW\*(C`read\*(C'\fR [perl #112826].
+.IP \(bu 4
+Time::Local has been upgraded to 1.2300.
+.Sp
+Seconds values greater than 59 but less than 60 no longer cause
+\&\f(CWtimegm()\fR and \f(CWtimelocal()\fR to croak.
+.IP \(bu 4
+Unicode::UCD has been upgraded to 0.53.
+.Sp
+This adds a function \fBall_casefolds()\fR
+that returns all the casefolds.
+.IP \(bu 4
+Win32 has been upgraded to 0.47.
+.Sp
+New APIs have been added for getting and setting the current code page.
+.SS "Removed Modules and Pragmata"
+.IX Subsection "Removed Modules and Pragmata"
+.IP \(bu 4
+Version::Requirements has been removed from the core distribution.  It is
+available under a different name: CPAN::Meta::Requirements.
+.SH Documentation
+.IX Header "Documentation"
+.SS "Changes to Existing Documentation"
+.IX Subsection "Changes to Existing Documentation"
+\fIperlcheat\fR
+.IX Subsection "perlcheat"
+.IP \(bu 4
+perlcheat has been reorganized, and a few new sections were added.
+.PP
+\fIperldata\fR
+.IX Subsection "perldata"
+.IP \(bu 4
+Now explicitly documents the behaviour of hash initializer lists that
+contain duplicate keys.
+.PP
+\fIperldiag\fR
+.IX Subsection "perldiag"
+.IP \(bu 4
+The explanation of symbolic references being prevented by "strict refs"
+now doesn't assume that the reader knows what symbolic references are.
+.PP
+\fIperlfaq\fR
+.IX Subsection "perlfaq"
+.IP \(bu 4
+perlfaq has been synchronized with version 5.0150040 from CPAN.
+.PP
+\fIperlfunc\fR
+.IX Subsection "perlfunc"
+.IP \(bu 4
+The return value of \f(CW\*(C`pipe\*(C'\fR is now documented.
+.IP \(bu 4
+Clarified documentation of \f(CW\*(C`our\*(C'\fR.
+.PP
+\fIperlop\fR
+.IX Subsection "perlop"
+.IP \(bu 4
+Loop control verbs (\f(CW\*(C`dump\*(C'\fR, \f(CW\*(C`goto\*(C'\fR, \f(CW\*(C`next\*(C'\fR, \f(CW\*(C`last\*(C'\fR and \f(CW\*(C`redo\*(C'\fR) have always
+had the same precedence as assignment operators, but this was not documented
+until now.
+.PP
+\fIDiagnostics\fR
+.IX Subsection "Diagnostics"
+.PP
+The following additions or changes have been made to diagnostic output,
+including warnings and fatal error messages.  For the complete list of
+diagnostic messages, see perldiag.
+.SS "New Diagnostics"
+.IX Subsection "New Diagnostics"
+\fINew Errors\fR
+.IX Subsection "New Errors"
+.IP \(bu 4
+Unterminated delimiter for here document
+.Sp
+This message now occurs when a here document label has an initial quotation
+mark but the final quotation mark is missing.
+.Sp
+This replaces a bogus and misleading error message about not finding the label
+itself [perl #114104].
+.IP \(bu 4
+panic: child pseudo-process was never scheduled
+.Sp
+This error is thrown when a child pseudo-process in the ithreads implementation
+on Windows was not scheduled within the time period allowed and therefore was
+not able to initialize properly [perl #88840].
+.IP \(bu 4
+Group name must start with a non-digit word character in regex; marked by <\-\- HERE in m/%s/
+.Sp
+This error has been added for \f(CW\*(C`(?&0)\*(C'\fR, which is invalid.  It used to
+produce an incomprehensible error message [perl #101666].
+.IP \(bu 4
+Can't use an undefined value as a subroutine reference
+.Sp
+Calling an undefined value as a subroutine now produces this error message.
+It used to, but was accidentally disabled, first in Perl 5.004 for
+non-magical variables, and then in Perl v5.14 for magical (e.g., tied)
+variables.  It has now been restored.  In the mean time, undef was treated
+as an empty string [perl #113576].
+.IP \(bu 4
+Experimental "%s" subs not enabled
+.Sp
+To use lexical subs, you must first enable them:
+.Sp
+.Vb 3
+\&    no warnings \*(Aqexperimental::lexical_subs\*(Aq;
+\&    use feature \*(Aqlexical_subs\*(Aq;
+\&    my sub foo { ... }
+.Ve
+.PP
+\fINew Warnings\fR
+.IX Subsection "New Warnings"
+.IP \(bu 4
+\&'Strings with code points over 0xFF may not be mapped into in-memory file handles'
+.IP \(bu 4
+\&'%s' resolved to '\eo{%s}%d'
+.IP \(bu 4
+\&'Trailing white-space in a charnames alias definition is deprecated'
+.IP \(bu 4
+\&'A sequence of multiple spaces in a charnames alias definition is deprecated'
+.IP \(bu 4
+\&'Passing malformed UTF\-8 to "%s" is deprecated'
+.IP \(bu 4
+Subroutine "&%s" is not available
+.Sp
+(W closure) During compilation, an inner named subroutine or eval is
+attempting to capture an outer lexical subroutine that is not currently
+available.  This can happen for one of two reasons.  First, the lexical
+subroutine may be declared in an outer anonymous subroutine that has not
+yet been created.  (Remember that named subs are created at compile time,
+while anonymous subs are created at run-time.)  For example,
+.Sp
+.Vb 1
+\&    sub { my sub a {...} sub f { \e&a } }
+.Ve
+.Sp
+At the time that f is created, it can't capture the current the "a" sub,
+since the anonymous subroutine hasn't been created yet.  Conversely, the
+following won't give a warning since the anonymous subroutine has by now
+been created and is live:
+.Sp
+.Vb 1
+\&    sub { my sub a {...} eval \*(Aqsub f { \e&a }\*(Aq }\->();
+.Ve
+.Sp
+The second situation is caused by an eval accessing a variable that has
+gone out of scope, for example,
+.Sp
+.Vb 5
+\&    sub f {
+\&        my sub a {...}
+\&        sub { eval \*(Aq\e&a\*(Aq }
+\&    }
+\&    f()\->();
+.Ve
+.Sp
+Here, when the '\e&a' in the eval is being compiled, f() is not currently
+being executed, so its &a is not available for capture.
+.IP \(bu 4
+"%s" subroutine &%s masks earlier declaration in same \f(CW%s\fR
+.Sp
+(W misc) A "my" or "state" subroutine has been redeclared in the
+current scope or statement, effectively eliminating all access to
+the previous instance.  This is almost always a typographical error.
+Note that the earlier subroutine will still exist until the end of
+the scope or until all closure references to it are destroyed.
+.IP \(bu 4
+The \f(CW%s\fR feature is experimental
+.Sp
+(S experimental) This warning is emitted if you enable an experimental
+feature via \f(CW\*(C`use feature\*(C'\fR.  Simply suppress the warning if you want
+to use the feature, but know that in doing so you are taking the risk
+of using an experimental feature which may change or be removed in a
+future Perl version:
+.Sp
+.Vb 2
+\&    no warnings "experimental::lexical_subs";
+\&    use feature "lexical_subs";
+.Ve
+.IP \(bu 4
+sleep(%u) too large
+.Sp
+(W overflow) You called \f(CW\*(C`sleep\*(C'\fR with a number that was larger than it can
+reliably handle and \f(CW\*(C`sleep\*(C'\fR probably slept for less time than requested.
+.IP \(bu 4
+Wide character in setenv
+.Sp
+Attempts to put wide characters into environment variables via \f(CW%ENV\fR now
+provoke this warning.
+.IP \(bu 4
+"Invalid negative number (%s) in chr"
+.Sp
+\&\f(CWchr()\fR now warns when passed a negative value [perl #83048].
+.IP \(bu 4
+"Integer overflow in srand"
+.Sp
+\&\f(CWsrand()\fR now warns when passed a value that doesn't fit in a \f(CW\*(C`UV\*(C'\fR (since the
+value will be truncated rather than overflowing) [perl #40605].
+.IP \(bu 4
+"\-i used with no filenames on the command line, reading from STDIN"
+.Sp
+Running perl with the \f(CW\*(C`\-i\*(C'\fR flag now warns if no input files are provided on
+the command line [perl #113410].
+.SS "Changes to Existing Diagnostics"
+.IX Subsection "Changes to Existing Diagnostics"
+.IP \(bu 4
+$* is no longer supported
+.Sp
+The warning that use of \f(CW$*\fR and \f(CW$#\fR is no longer supported is now
+generated for every location that references them.  Previously it would fail
+to be generated if another variable using the same typeglob was seen first
+(e.g. \f(CW\*(C`@*\*(C'\fR before \f(CW$*\fR), and would not be generated for the second and
+subsequent uses.  (It's hard to fix the failure to generate warnings at all
+without also generating them every time, and warning every time is
+consistent with the warnings that \f(CW$[\fR used to generate.)
+.IP \(bu 4
+The warnings for \f(CW\*(C`\eb{\*(C'\fR and \f(CW\*(C`\eB{\*(C'\fR were added.  They are a deprecation
+warning which should be turned off by that category.  One should not
+have to turn off regular regexp warnings as well to get rid of these.
+.IP \(bu 4
+Constant(%s): Call to &{$^H{%s}} did not return a defined value
+.Sp
+Constant overloading that returns \f(CW\*(C`undef\*(C'\fR results in this error message.
+For numeric constants, it used to say "Constant(undef)".  "undef" has been
+replaced with the number itself.
+.IP \(bu 4
+The error produced when a module cannot be loaded now includes a hint that
+the module may need to be installed: "Can't locate hopping.pm in \f(CW@INC\fR (you
+may need to install the hopping module) (@INC contains: ...)"
+.IP \(bu 4
+vector argument not supported with alpha versions
+.Sp
+This warning was not suppressible, even with \f(CW\*(C`no warnings\*(C'\fR.  Now it is
+suppressible, and has been moved from the "internal" category to the
+"printf" category.
+.IP \(bu 4
+\&\f(CW\*(C`Can\*(Aqt do {n,m} with n > m in regex; marked by <\-\- HERE in m/%s/\*(C'\fR
+.Sp
+This fatal error has been turned into a warning that reads:
+.Sp
+Quantifier {n,m} with n > m can't match in regex
+.Sp
+(W regexp) Minima should be less than or equal to maxima.  If you really want
+your regexp to match something 0 times, just put {0}.
+.IP \(bu 4
+The "Runaway prototype" warning that occurs in bizarre cases has been
+removed as being unhelpful and inconsistent.
+.IP \(bu 4
+The "Not a format reference" error has been removed, as the only case in
+which it could be triggered was a bug.
+.IP \(bu 4
+The "Unable to create sub named \f(CW%s\fR" error has been removed for the same
+reason.
+.IP \(bu 4
+The 'Can't use "my \f(CW%s\fR" in sort comparison' error has been downgraded to a
+warning, '"my \f(CW%s\fR" used in sort comparison' (with 'state' instead of 'my'
+for state variables).  In addition, the heuristics for guessing whether
+lexical \f(CW$a\fR or \f(CW$b\fR has been misused have been improved to generate fewer
+false positives.  Lexical \f(CW$a\fR and \f(CW$b\fR are no longer disallowed if they are
+outside the sort block.  Also, a named unary or list operator inside the
+sort block no longer causes the \f(CW$a\fR or \f(CW$b\fR to be ignored [perl #86136].
+.SH "Utility Changes"
+.IX Header "Utility Changes"
+\fIh2xs\fR
+.IX Subsection "h2xs"
+.IP \(bu 4
+\&\fIh2xs\fR no longer produces invalid code for empty defines.  [perl #20636]
+.SH "Configuration and Compilation"
+.IX Header "Configuration and Compilation"
+.IP \(bu 4
+Added \f(CW\*(C`useversionedarchname\*(C'\fR option to Configure
+.Sp
+When set, it includes 'api_versionstring' in 'archname'. E.g.
+x86_64\-linux\-5.13.6\-thread\-multi.  It is unset by default.
+.Sp
+This feature was requested by Tim Bunce, who observed that
+\&\f(CW\*(C`INSTALL_BASE\*(C'\fR creates a library structure that does not
+differentiate by perl version.  Instead, it places architecture
+specific files in "$install_base/lib/perl5/$archname".  This makes
+it difficult to use a common \f(CW\*(C`INSTALL_BASE\*(C'\fR library path with
+multiple versions of perl.
+.Sp
+By setting \f(CW\*(C`\-Duseversionedarchname\*(C'\fR, the \f(CW$archname\fR will be
+distinct for architecture \fIand\fR API version, allowing mixed use of
+\&\f(CW\*(C`INSTALL_BASE\*(C'\fR.
+.IP \(bu 4
+Add a \f(CW\*(C`PERL_NO_INLINE_FUNCTIONS\*(C'\fR option
+.Sp
+If \f(CW\*(C`PERL_NO_INLINE_FUNCTIONS\*(C'\fR is defined, don't include "inline.h"
+.Sp
+This permits test code to include the perl headers for definitions without
+creating a link dependency on the perl library (which may not exist yet).
+.IP \(bu 4
+Configure will honour the external \f(CW\*(C`MAILDOMAIN\*(C'\fR environment variable, if set.
+.IP \(bu 4
+\&\f(CW\*(C`installman\*(C'\fR no longer ignores the silent option
+.IP \(bu 4
+Both \f(CW\*(C`META.yml\*(C'\fR and \f(CW\*(C`META.json\*(C'\fR files are now included in the distribution.
+.IP \(bu 4
+\&\fIConfigure\fR will now correctly detect \f(CWisblank()\fR when compiling with a C++
+compiler.
+.IP \(bu 4
+The pager detection in \fIConfigure\fR has been improved to allow responses which
+specify options after the program name, e.g. \fB/usr/bin/less \-R\fR, if the user
+accepts the default value.  This helps \fBperldoc\fR when handling ANSI escapes
+[perl #72156].
+.SH Testing
+.IX Header "Testing"
+.IP \(bu 4
+The test suite now has a section for tests that require very large amounts
+of memory.  These tests won't run by default; they can be enabled by
+setting the \f(CW\*(C`PERL_TEST_MEMORY\*(C'\fR environment variable to the number of
+gibibytes of memory that may be safely used.
+.SH "Platform Support"
+.IX Header "Platform Support"
+.SS "Discontinued Platforms"
+.IX Subsection "Discontinued Platforms"
+.IP BeOS 4
+.IX Item "BeOS"
+BeOS was an operating system for personal computers developed by Be Inc,
+initially for their BeBox hardware. The OS Haiku was written as an open
+source replacement for/continuation of BeOS, and its perl port is current and
+actively maintained.
+.IP "UTS Global" 4
+.IX Item "UTS Global"
+Support code relating to UTS global has been removed.  UTS was a mainframe
+version of System V created by Amdahl, subsequently sold to UTS Global.  The
+port has not been touched since before Perl v5.8.0, and UTS Global is now
+defunct.
+.IP VM/ESA 4
+.IX Item "VM/ESA"
+Support for VM/ESA has been removed. The port was tested on 2.3.0, which
+IBM ended service on in March 2002. 2.4.0 ended service in June 2003, and
+was superseded by Z/VM. The current version of Z/VM is V6.2.0, and scheduled
+for end of service on 2015/04/30.
+.IP MPE/IX 4
+.IX Item "MPE/IX"
+Support for MPE/IX has been removed.
+.IP EPOC 4
+.IX Item "EPOC"
+Support code relating to EPOC has been removed.  EPOC was a family of
+operating systems developed by Psion for mobile devices.  It was the
+predecessor of Symbian.  The port was last updated in April 2002.
+.IP Rhapsody 4
+.IX Item "Rhapsody"
+Support for Rhapsody has been removed.
+.SS "Platform-Specific Notes"
+.IX Subsection "Platform-Specific Notes"
+\fIAIX\fR
+.IX Subsection "AIX"
+.PP
+Configure now always adds \f(CW\*(C`\-qlanglvl=extc99\*(C'\fR to the CC flags on AIX when
+using xlC.  This will make it easier to compile a number of XS-based modules
+that assume C99 [perl #113778].
+.PP
+\fIclang++\fR
+.IX Subsection "clang++"
+.PP
+There is now a workaround for a compiler bug that prevented compiling
+with clang++ since Perl v5.15.7 [perl #112786].
+.PP
+\fIC++\fR
+.IX Subsection "C++"
+.PP
+When compiling the Perl core as C++ (which is only semi-supported), the
+mathom functions are now compiled as \f(CW\*(C`extern "C"\*(C'\fR, to ensure proper
+binary compatibility.  (However, binary compatibility isn't generally
+guaranteed anyway in the situations where this would matter.)
+.PP
+\fIDarwin\fR
+.IX Subsection "Darwin"
+.PP
+Stop hardcoding an alignment on 8 byte boundaries to fix builds using
+\&\-Dusemorebits.
+.PP
+\fIHaiku\fR
+.IX Subsection "Haiku"
+.PP
+Perl should now work out of the box on Haiku R1 Alpha 4.
+.PP
+\fIMidnightBSD\fR
+.IX Subsection "MidnightBSD"
+.PP
+\&\f(CW\*(C`libc_r\*(C'\fR was removed from recent versions of MidnightBSD and older versions
+work better with \f(CW\*(C`pthread\*(C'\fR. Threading is now enabled using \f(CW\*(C`pthread\*(C'\fR which
+corrects build errors with threading enabled on 0.4\-CURRENT.
+.PP
+\fISolaris\fR
+.IX Subsection "Solaris"
+.PP
+In Configure, avoid running sed commands with flags not supported on Solaris.
+.PP
+\fIVMS\fR
+.IX Subsection "VMS"
+.IP \(bu 4
+Where possible, the case of filenames and command-line arguments is now
+preserved by enabling the CRTL features \f(CW\*(C`DECC$EFS_CASE_PRESERVE\*(C'\fR and
+\&\f(CW\*(C`DECC$ARGV_PARSE_STYLE\*(C'\fR at start-up time.  The latter only takes effect
+when extended parse is enabled in the process from which Perl is run.
+.IP \(bu 4
+The character set for Extended Filename Syntax (EFS) is now enabled by default
+on VMS.  Among other things, this provides better handling of dots in directory
+names, multiple dots in filenames, and spaces in filenames.  To obtain the old
+behavior, set the logical name \f(CW\*(C`DECC$EFS_CHARSET\*(C'\fR to \f(CW\*(C`DISABLE\*(C'\fR.
+.IP \(bu 4
+Fixed linking on builds configured with \f(CW\*(C`\-Dusemymalloc=y\*(C'\fR.
+.IP \(bu 4
+Experimental support for building Perl with the HP C++ compiler is available
+by configuring with \f(CW\*(C`\-Dusecxx\*(C'\fR.
+.IP \(bu 4
+All C header files from the top-level directory of the distribution are now
+installed on VMS, providing consistency with a long-standing practice on other
+platforms. Previously only a subset were installed, which broke non-core
+extension builds for extensions that depended on the missing include files.
+.IP \(bu 4
+Quotes are now removed from the command verb (but not the parameters) for
+commands spawned via \f(CW\*(C`system\*(C'\fR, backticks, or a piped \f(CW\*(C`open\*(C'\fR.  Previously,
+quotes on the verb were passed through to DCL, which would fail to recognize
+the command.  Also, if the verb is actually a path to an image or command
+procedure on an ODS\-5 volume, quoting it now allows the path to contain spaces.
+.IP \(bu 4
+The \fBa2p\fR build has been fixed for the HP C++ compiler on OpenVMS.
+.PP
+\fIWin32\fR
+.IX Subsection "Win32"
+.IP \(bu 4
+Perl can now be built using Microsoft's Visual C++ 2012 compiler by specifying
+CCTYPE=MSVC110 (or MSVC110FREE if you are using the free Express edition for
+Windows Desktop) in \fIwin32/Makefile\fR.
+.IP \(bu 4
+The option to build without \f(CW\*(C`USE_SOCKETS_AS_HANDLES\*(C'\fR has been removed.
+.IP \(bu 4
+Fixed a problem where perl could crash while cleaning up threads (including the
+main thread) in threaded debugging builds on Win32 and possibly other platforms
+[perl #114496].
+.IP \(bu 4
+A rare race condition that would lead to sleep taking more
+time than requested, and possibly even hanging, has been fixed [perl #33096].
+.IP \(bu 4
+\&\f(CW\*(C`link\*(C'\fR on Win32 now attempts to set \f(CW$!\fR to more appropriate values
+based on the Win32 API error code. [perl #112272]
+.Sp
+Perl no longer mangles the environment block, e.g. when launching a new
+sub-process, when the environment contains non-ASCII characters. Known
+problems still remain, however, when the environment contains characters
+outside of the current ANSI codepage (e.g. see the item about Unicode in
+\&\f(CW%ENV\fR in <http://perl5.git.perl.org/perl.git/blob/HEAD:/Porting/todo.pod>).
+[perl #113536]
+.IP \(bu 4
+Building perl with some Windows compilers used to fail due to a problem
+with miniperl's \f(CW\*(C`glob\*(C'\fR operator (which uses the \f(CW\*(C`perlglob\*(C'\fR program)
+deleting the PATH environment variable [perl #113798].
+.IP \(bu 4
+A new makefile option, \f(CW\*(C`USE_64_BIT_INT\*(C'\fR, has been added to the Windows
+makefiles.  Set this to "define" when building a 32\-bit perl if you want
+it to use 64\-bit integers.
+.Sp
+Machine code size reductions, already made to the DLLs of XS modules in
+Perl v5.17.2, have now been extended to the perl DLL itself.
+.Sp
+Building with VC++ 6.0 was inadvertently broken in Perl v5.17.2 but has
+now been fixed again.
+.PP
+\fIWinCE\fR
+.IX Subsection "WinCE"
+.PP
+Building on WinCE is now possible once again, although more work is required
+to fully restore a clean build.
+.SH "Internal Changes"
+.IX Header "Internal Changes"
+.IP \(bu 4
+Synonyms for the misleadingly named \f(CWav_len()\fR have been created:
+\&\f(CWav_top_index()\fR and \f(CW\*(C`av_tindex\*(C'\fR.  All three of these return the
+number of the highest index in the array, not the number of elements it
+contains.
+.IP \(bu 4
+\&\fBSvUPGRADE()\fR is no longer an expression. Originally this macro (and its
+underlying function, \fBsv_upgrade()\fR) were documented as boolean, although
+in reality they always croaked on error and never returned false. In 2005
+the documentation was updated to specify a void return value, but
+\&\fBSvUPGRADE()\fR was left always returning 1 for backwards compatibility. This
+has now been removed, and \fBSvUPGRADE()\fR is now a statement with no return
+value.
+.Sp
+So this is now a syntax error:
+.Sp
+.Vb 1
+\&    if (!SvUPGRADE(sv)) { croak(...); }
+.Ve
+.Sp
+If you have code like that, simply replace it with
+.Sp
+.Vb 1
+\&    SvUPGRADE(sv);
+.Ve
+.Sp
+or to avoid compiler warnings with older perls, possibly
+.Sp
+.Vb 1
+\&    (void)SvUPGRADE(sv);
+.Ve
+.IP \(bu 4
+Perl has a new copy-on-write mechanism that allows any SvPOK scalar to be
+upgraded to a copy-on-write scalar.  A reference count on the string buffer
+is stored in the string buffer itself.  This feature is \fBnot enabled by
+default\fR.
+.Sp
+It can be enabled in a perl build by running \fIConfigure\fR with
+\&\fB\-Accflags=\-DPERL_NEW_COPY_ON_WRITE\fR, and we would encourage XS authors
+to try their code with such an enabled perl, and provide feedback.
+Unfortunately, there is not yet a good guide to updating XS code to cope
+with COW.  Until such a document is available, consult the perl5\-porters
+mailing list.
+.Sp
+It breaks a few XS modules by allowing copy-on-write scalars to go
+through code paths that never encountered them before.
+.IP \(bu 4
+Copy-on-write no longer uses the SvFAKE and SvREADONLY flags.  Hence,
+SvREADONLY indicates a true read-only SV.
+.Sp
+Use the SvIsCOW macro (as before) to identify a copy-on-write scalar.
+.IP \(bu 4
+\&\f(CW\*(C`PL_glob_index\*(C'\fR is gone.
+.IP \(bu 4
+The private Perl_croak_no_modify has had its context parameter removed.  It is
+now has a void prototype.  Users of the public API croak_no_modify remain
+unaffected.
+.IP \(bu 4
+Copy-on-write (shared hash key) scalars are no longer marked read-only.
+\&\f(CW\*(C`SvREADONLY\*(C'\fR returns false on such an SV, but \f(CW\*(C`SvIsCOW\*(C'\fR still returns
+true.
+.IP \(bu 4
+A new op type, \f(CW\*(C`OP_PADRANGE\*(C'\fR has been introduced.  The perl peephole
+optimiser will, where possible, substitute a single padrange op for a
+pushmark followed by one or more pad ops, and possibly also skipping list
+and nextstate ops.  In addition, the op can carry out the tasks associated
+with the RHS of a \f(CW\*(C`my(...) = @_\*(C'\fR assignment, so those ops may be optimised
+away too.
+.IP \(bu 4
+Case-insensitive matching inside a [bracketed] character class with a
+multi-character fold no longer excludes one of the possibilities in the
+circumstances that it used to. [perl #89774].
+.IP \(bu 4
+\&\f(CW\*(C`PL_formfeed\*(C'\fR has been removed.
+.IP \(bu 4
+The regular expression engine no longer reads one byte past the end of the
+target string.  While for all internally well-formed scalars this should
+never have been a problem, this change facilitates clever tricks with
+string buffers in CPAN modules.  [perl #73542]
+.IP \(bu 4
+Inside a BEGIN block, \f(CW\*(C`PL_compcv\*(C'\fR now points to the currently-compiling
+subroutine, rather than the BEGIN block itself.
+.IP \(bu 4
+\&\f(CW\*(C`mg_length\*(C'\fR has been deprecated.
+.IP \(bu 4
+\&\f(CW\*(C`sv_len\*(C'\fR now always returns a byte count and \f(CW\*(C`sv_len_utf8\*(C'\fR a character
+count.  Previously, \f(CW\*(C`sv_len\*(C'\fR and \f(CW\*(C`sv_len_utf8\*(C'\fR were both buggy and would
+sometimes returns bytes and sometimes characters.  \f(CW\*(C`sv_len_utf8\*(C'\fR no longer
+assumes that its argument is in UTF\-8.  Neither of these creates UTF\-8 caches
+for tied or overloaded values or for non-PVs any more.
+.IP \(bu 4
+\&\f(CW\*(C`sv_mortalcopy\*(C'\fR now copies string buffers of shared hash key scalars when
+called from XS modules [perl #79824].
+.IP \(bu 4
+The new \f(CW\*(C`RXf_MODIFIES_VARS\*(C'\fR flag can be set by custom regular expression
+engines to indicate that the execution of the regular expression may cause
+variables to be modified.  This lets \f(CW\*(C`s///\*(C'\fR know to skip certain
+optimisations.  Perl's own regular expression engine sets this flag for the
+special backtracking verbs that set \f(CW$REGMARK\fR and \f(CW$REGERROR\fR.
+.IP \(bu 4
+The APIs for accessing lexical pads have changed considerably.
+.Sp
+\&\f(CW\*(C`PADLIST\*(C'\fRs are now longer \f(CW\*(C`AV\*(C'\fRs, but their own type instead.
+\&\f(CW\*(C`PADLIST\*(C'\fRs now contain a \f(CW\*(C`PAD\*(C'\fR and a \f(CW\*(C`PADNAMELIST\*(C'\fR of \f(CW\*(C`PADNAME\*(C'\fRs,
+rather than \f(CW\*(C`AV\*(C'\fRs for the pad and the list of pad names.  \f(CW\*(C`PAD\*(C'\fRs,
+\&\f(CW\*(C`PADNAMELIST\*(C'\fRs, and \f(CW\*(C`PADNAME\*(C'\fRs are to be accessed as such through the
+newly added pad API instead of the plain \f(CW\*(C`AV\*(C'\fR and \f(CW\*(C`SV\*(C'\fR APIs.  See
+perlapi for details.
+.IP \(bu 4
+In the regex API, the numbered capture callbacks are passed an index
+indicating what match variable is being accessed. There are special
+index values for the \f(CW\*(C`$\`, $&, $&\*(C'\fR variables. Previously the same three
+values were used to retrieve \f(CW\*(C`${^PREMATCH}, ${^MATCH}, ${^POSTMATCH}\*(C'\fR
+too, but these have now been assigned three separate values. See
+"Numbered capture callbacks" in perlreapi.
+.IP \(bu 4
+\&\f(CW\*(C`PL_sawampersand\*(C'\fR was previously a boolean indicating that any of
+\&\f(CW\*(C`$\`, $&, $&\*(C'\fR had been seen; it now contains three one-bit flags
+indicating the presence of each of the variables individually.
+.IP \(bu 4
+The \f(CW\*(C`CV *\*(C'\fR typemap entry now supports \f(CW\*(C`&{}\*(C'\fR overloading and typeglobs,
+just like \f(CW\*(C`&{...}\*(C'\fR [perl #96872].
+.IP \(bu 4
+The \f(CW\*(C`SVf_AMAGIC\*(C'\fR flag to indicate overloading is now on the stash, not the
+object.  It is now set automatically whenever a method or \f(CW@ISA\fR changes, so
+its meaning has changed, too.  It now means "potentially overloaded".  When
+the overload table is calculated, the flag is automatically turned off if
+there is no overloading, so there should be no noticeable slowdown.
+.Sp
+The staleness of the overload tables is now checked when overload methods
+are invoked, rather than during \f(CW\*(C`bless\*(C'\fR.
+.Sp
+"A" magic is gone.  The changes to the handling of the \f(CW\*(C`SVf_AMAGIC\*(C'\fR flag
+eliminate the need for it.
+.Sp
+\&\f(CW\*(C`PL_amagic_generation\*(C'\fR has been removed as no longer necessary.  For XS
+modules, it is now a macro alias to \f(CW\*(C`PL_na\*(C'\fR.
+.Sp
+The fallback overload setting is now stored in a stash entry separate from
+overloadedness itself.
+.IP \(bu 4
+The character-processing code has been cleaned up in places.  The changes
+should be operationally invisible.
+.IP \(bu 4
+The \f(CW\*(C`study\*(C'\fR function was made a no-op in v5.16.  It was simply disabled via
+a \f(CW\*(C`return\*(C'\fR statement; the code was left in place.  Now the code supporting
+what \f(CW\*(C`study\*(C'\fR used to do has been removed.
+.IP \(bu 4
+Under threaded perls, there is no longer a separate PV allocated for every
+COP to store its package name (\f(CW\*(C`cop\->stashpv\*(C'\fR).  Instead, there is an
+offset (\f(CW\*(C`cop\->stashoff\*(C'\fR) into the new \f(CW\*(C`PL_stashpad\*(C'\fR array, which
+holds stash pointers.
+.IP \(bu 4
+In the pluggable regex API, the \f(CW\*(C`regexp_engine\*(C'\fR struct has acquired a new
+field \f(CW\*(C`op_comp\*(C'\fR, which is currently just for perl's internal use, and
+should be initialized to NULL by other regex plugin modules.
+.IP \(bu 4
+A new function \f(CW\*(C`alloccopstash\*(C'\fR has been added to the API, but is considered
+experimental.  See perlapi.
+.IP \(bu 4
+Perl used to implement get magic in a way that would sometimes hide bugs in
+code that could call \fBmg_get()\fR too many times on magical values.  This hiding of
+errors no longer occurs, so long-standing bugs may become visible now.  If
+you see magic-related errors in XS code, check to make sure it, together
+with the Perl API functions it uses, calls \fBmg_get()\fR only once on \fBSvGMAGICAL()\fR
+values.
+.IP \(bu 4
+OP allocation for CVs now uses a slab allocator.  This simplifies
+memory management for OPs allocated to a CV, so cleaning up after a
+compilation error is simpler and safer [perl #111462][perl #112312].
+.IP \(bu 4
+\&\f(CW\*(C`PERL_DEBUG_READONLY_OPS\*(C'\fR has been rewritten to work with the new slab
+allocator, allowing it to catch more violations than before.
+.IP \(bu 4
+The old slab allocator for ops, which was only enabled for \f(CW\*(C`PERL_IMPLICIT_SYS\*(C'\fR
+and \f(CW\*(C`PERL_DEBUG_READONLY_OPS\*(C'\fR, has been retired.
+.SH "Selected Bug Fixes"
+.IX Header "Selected Bug Fixes"
+.IP \(bu 4
+Here document terminators no longer require a terminating newline character when
+they occur at the end of a file.  This was already the case at the end of a
+string eval [perl #65838].
+.IP \(bu 4
+\&\f(CW\*(C`\-DPERL_GLOBAL_STRUCT\*(C'\fR builds now free the global struct \fBafter\fR
+they've finished using it.
+.IP \(bu 4
+A trailing '/' on a path in \f(CW@INC\fR will no longer have an additional '/'
+appended.
+.IP \(bu 4
+The \f(CW\*(C`:crlf\*(C'\fR layer now works when unread data doesn't fit into its own
+buffer. [perl #112244].
+.IP \(bu 4
+\&\f(CWungetc()\fR now handles UTF\-8 encoded data. [perl #116322].
+.IP \(bu 4
+A bug in the core typemap caused any C types that map to the T_BOOL core
+typemap entry to not be set, updated, or modified when the T_BOOL variable was
+used in an OUTPUT: section with an exception for RETVAL. T_BOOL in an INPUT:
+section was not affected. Using a T_BOOL return type for an XSUB (RETVAL)
+was not affected. A side effect of fixing this bug is, if a T_BOOL is specified
+in the OUTPUT: section (which previous did nothing to the SV), and a read only
+SV (literal) is passed to the XSUB, croaks like "Modification of a read-only
+value attempted" will happen. [perl #115796]
+.IP \(bu 4
+On many platforms, providing a directory name as the script name caused perl
+to do nothing and report success.  It should now universally report an error
+and exit nonzero. [perl #61362]
+.IP \(bu 4
+\&\f(CW\*(C`sort {undef} ...\*(C'\fR under fatal warnings no longer crashes.  It had
+begun crashing in Perl v5.16.
+.IP \(bu 4
+Stashes blessed into each other
+(\f(CW\*(C`bless \e%Foo::, \*(AqBar\*(Aq; bless \e%Bar::, \*(AqFoo\*(Aq\*(C'\fR) no longer result in double
+frees.  This bug started happening in Perl v5.16.
+.IP \(bu 4
+Numerous memory leaks have been fixed, mostly involving fatal warnings and
+syntax errors.
+.IP \(bu 4
+Some failed regular expression matches such as \f(CW\*(C`\*(Aqf\*(Aq =~ /../g\*(C'\fR were not
+resetting \f(CW\*(C`pos\*(C'\fR.  Also, "match-once" patterns (\f(CW\*(C`m?...?g\*(C'\fR) failed to reset
+it, too, when invoked a second time [perl #23180].
+.IP \(bu 4
+Several bugs involving \f(CW\*(C`local *ISA\*(C'\fR and \f(CW\*(C`local *Foo::\*(C'\fR causing stale
+MRO caches have been fixed.
+.IP \(bu 4
+Defining a subroutine when its typeglob has been aliased no longer results
+in stale method caches.  This bug was introduced in Perl v5.10.
+.IP \(bu 4
+Localising a typeglob containing a subroutine when the typeglob's package
+has been deleted from its parent stash no longer produces an error.  This
+bug was introduced in Perl v5.14.
+.IP \(bu 4
+Under some circumstances, \f(CW\*(C`local *method=...\*(C'\fR would fail to reset method
+caches upon scope exit.
+.IP \(bu 4
+\&\f(CW\*(C`/[.foo.]/\*(C'\fR is no longer an error, but produces a warning (as before) and
+is treated as \f(CW\*(C`/[.fo]/\*(C'\fR [perl #115818].
+.IP \(bu 4
+\&\f(CW\*(C`goto $tied_var\*(C'\fR now calls FETCH before deciding what type of goto
+(subroutine or label) this is.
+.IP \(bu 4
+Renaming packages through glob assignment
+(\f(CW\*(C`*Foo:: = *Bar::; *Bar:: = *Baz::\*(C'\fR) in combination with \f(CW\*(C`m?...?\*(C'\fR and
+\&\f(CW\*(C`reset\*(C'\fR no longer makes threaded builds crash.
+.IP \(bu 4
+A number of bugs related to assigning a list to hash have been fixed. Many of
+these involve lists with repeated keys like \f(CW\*(C`(1, 1, 1, 1)\*(C'\fR.
+.RS 4
+.IP \(bu 4
+The expression \f(CW\*(C`scalar(%h = (1, 1, 1, 1))\*(C'\fR now returns \f(CW4\fR, not \f(CW2\fR.
+.IP \(bu 4
+The return value of \f(CW\*(C`%h = (1, 1, 1)\*(C'\fR in list context was wrong. Previously
+this would return \f(CW\*(C`(1, undef, 1)\*(C'\fR, now it returns \f(CW\*(C`(1, undef)\*(C'\fR.
+.IP \(bu 4
+Perl now issues the same warning on \f(CW\*(C`($s, %h) = (1, {})\*(C'\fR as it does for
+\&\f(CW\*(C`(%h) = ({})\*(C'\fR, "Reference found where even-sized list expected".
+.IP \(bu 4
+A number of additional edge cases in list assignment to hashes were
+corrected. For more details see commit 23b7025ebc.
+.RE
+.RS 4
+.RE
+.IP \(bu 4
+Attributes applied to lexical variables no longer leak memory.
+[perl #114764]
+.IP \(bu 4
+\&\f(CW\*(C`dump\*(C'\fR, \f(CW\*(C`goto\*(C'\fR, \f(CW\*(C`last\*(C'\fR, \f(CW\*(C`next\*(C'\fR, \f(CW\*(C`redo\*(C'\fR or \f(CW\*(C`require\*(C'\fR followed by a
+bareword (or version) and then an infix operator is no longer a syntax
+error.  It used to be for those infix operators (like \f(CW\*(C`+\*(C'\fR) that have a
+different meaning where a term is expected.  [perl #105924]
+.IP \(bu 4
+\&\f(CW\*(C`require a::b . 1\*(C'\fR and \f(CW\*(C`require a::b + 1\*(C'\fR no longer produce erroneous
+ambiguity warnings.  [perl #107002]
+.IP \(bu 4
+Class method calls are now allowed on any string, and not just strings
+beginning with an alphanumeric character.  [perl #105922]
+.IP \(bu 4
+An empty pattern created with \f(CW\*(C`qr//\*(C'\fR used in \f(CW\*(C`m///\*(C'\fR no longer triggers
+the "empty pattern reuses last pattern" behaviour.  [perl #96230]
+.IP \(bu 4
+Tying a hash during iteration no longer results in a memory leak.
+.IP \(bu 4
+Freeing a tied hash during iteration no longer results in a memory leak.
+.IP \(bu 4
+List assignment to a tied array or hash that dies on STORE no longer
+results in a memory leak.
+.IP \(bu 4
+If the hint hash (\f(CW\*(C`%^H\*(C'\fR) is tied, compile-time scope entry (which copies
+the hint hash) no longer leaks memory if FETCH dies.  [perl #107000]
+.IP \(bu 4
+Constant folding no longer inappropriately triggers the special
+\&\f(CW\*(C`split " "\*(C'\fR behaviour.  [perl #94490]
+.IP \(bu 4
+\&\f(CW\*(C`defined scalar(@array)\*(C'\fR, \f(CW\*(C`defined do { &foo }\*(C'\fR, and similar constructs
+now treat the argument to \f(CW\*(C`defined\*(C'\fR as a simple scalar.  [perl #97466]
+.IP \(bu 4
+Running a custom debugging that defines no \f(CW*DB::DB\fR glob or provides a
+subroutine stub for \f(CW&DB::DB\fR no longer results in a crash, but an error
+instead.  [perl #114990]
+.IP \(bu 4
+\&\f(CW\*(C`reset ""\*(C'\fR now matches its documentation.  \f(CW\*(C`reset\*(C'\fR only resets \f(CW\*(C`m?...?\*(C'\fR
+patterns when called with no argument.  An empty string for an argument now
+does nothing.  (It used to be treated as no argument.)  [perl #97958]
+.IP \(bu 4
+\&\f(CW\*(C`printf\*(C'\fR with an argument returning an empty list no longer reads past the
+end of the stack, resulting in erratic behaviour.  [perl #77094]
+.IP \(bu 4
+\&\f(CW\*(C`\-\-subname\*(C'\fR no longer produces erroneous ambiguity warnings.
+[perl #77240]
+.IP \(bu 4
+\&\f(CW\*(C`v10\*(C'\fR is now allowed as a label or package name.  This was inadvertently
+broken when v\-strings were added in Perl v5.6.  [perl #56880]
+.IP \(bu 4
+\&\f(CW\*(C`length\*(C'\fR, \f(CW\*(C`pos\*(C'\fR, \f(CW\*(C`substr\*(C'\fR and \f(CW\*(C`sprintf\*(C'\fR could be confused by ties,
+overloading, references and typeglobs if the stringification of such
+changed the internal representation to or from UTF\-8.  [perl #114410]
+.IP \(bu 4
+utf8::encode now calls FETCH and STORE on tied variables.  utf8::decode now
+calls STORE (it was already calling FETCH).
+.IP \(bu 4
+\&\f(CW\*(C`$tied =~ s/$non_utf8/$utf8/\*(C'\fR no longer loops infinitely if the tied
+variable returns a Latin\-1 string, shared hash key scalar, or reference or
+typeglob that stringifies as ASCII or Latin\-1.  This was a regression from
+v5.12.
+.IP \(bu 4
+\&\f(CW\*(C`s///\*(C'\fR without /e is now better at detecting when it needs to forego
+certain optimisations, fixing some buggy cases:
+.RS 4
+.IP \(bu 4
+Match variables in certain constructs (\f(CW\*(C`&&\*(C'\fR, \f(CW\*(C`||\*(C'\fR, \f(CW\*(C`..\*(C'\fR and others) in
+the replacement part; e.g., \f(CW\*(C`s/(.)/$l{$a||$1}/g\*(C'\fR.  [perl #26986]
+.IP \(bu 4
+Aliases to match variables in the replacement.
+.IP \(bu 4
+\&\f(CW$REGERROR\fR or \f(CW$REGMARK\fR in the replacement.  [perl #49190]
+.IP \(bu 4
+An empty pattern (\f(CW\*(C`s//$foo/\*(C'\fR) that causes the last-successful pattern to
+be used, when that pattern contains code blocks that modify the variables
+in the replacement.
+.RE
+.RS 4
+.RE
+.IP \(bu 4
+The taintedness of the replacement string no longer affects the taintedness
+of the return value of \f(CW\*(C`s///e\*(C'\fR.
+.IP \(bu 4
+The \f(CW$|\fR autoflush variable is created on-the-fly when needed.  If this
+happened (e.g., if it was mentioned in a module or eval) when the
+currently-selected filehandle was a typeglob with an empty IO slot, it used
+to crash.  [perl #115206]
+.IP \(bu 4
+Line numbers at the end of a string eval are no longer off by one.
+[perl #114658]
+.IP \(bu 4
+\&\f(CW@INC\fR filters (subroutines returned by subroutines in \f(CW@INC\fR) that set \f(CW$_\fR to a
+copy-on-write scalar no longer cause the parser to modify that string
+buffer in place.
+.IP \(bu 4
+\&\f(CWlength($object)\fR no longer returns the undefined value if the object has
+string overloading that returns undef.  [perl #115260]
+.IP \(bu 4
+The use of \f(CW\*(C`PL_stashcache\*(C'\fR, the stash name lookup cache for method calls, has
+been restored,
+.Sp
+Commit da6b625f78f5f133 in August 2011 inadvertently broke the code that looks
+up values in \f(CW\*(C`PL_stashcache\*(C'\fR. As it's only a cache, quite correctly everything
+carried on working without it.
+.IP \(bu 4
+The error "Can't localize through a reference" had disappeared in v5.16.0
+when \f(CW\*(C`local %$ref\*(C'\fR appeared on the last line of an lvalue subroutine.
+This error disappeared for \f(CW\*(C`\elocal %$ref\*(C'\fR in perl v5.8.1.  It has now
+been restored.
+.IP \(bu 4
+The parsing of here-docs has been improved significantly, fixing several
+parsing bugs and crashes and one memory leak, and correcting wrong
+subsequent line numbers under certain conditions.
+.IP \(bu 4
+Inside an eval, the error message for an unterminated here-doc no longer
+has a newline in the middle of it [perl #70836].
+.IP \(bu 4
+A substitution inside a substitution pattern (\f(CW\*(C`s/${s|||}//\*(C'\fR) no longer
+confuses the parser.
+.IP \(bu 4
+It may be an odd place to allow comments, but \f(CW\*(C`s//"" # hello/e\*(C'\fR has
+always worked, \fIunless\fR there happens to be a null character before the
+first #.  Now it works even in the presence of nulls.
+.IP \(bu 4
+An invalid range in \f(CW\*(C`tr///\*(C'\fR or \f(CW\*(C`y///\*(C'\fR no longer results in a memory leak.
+.IP \(bu 4
+String eval no longer treats a semicolon-delimited quote-like operator at
+the very end (\f(CW\*(C`eval \*(Aqq;;\*(Aq\*(C'\fR) as a syntax error.
+.IP \(bu 4
+\&\f(CW\*(C`warn {$_ => 1} + 1\*(C'\fR is no longer a syntax error.  The parser used to
+get confused with certain list operators followed by an anonymous hash and
+then an infix operator that shares its form with a unary operator.
+.IP \(bu 4
+\&\f(CW\*(C`(caller $n)[6]\*(C'\fR (which gives the text of the eval) used to return the
+actual parser buffer.  Modifying it could result in crashes.  Now it always
+returns a copy.  The string returned no longer has "\en;" tacked on to the
+end.  The returned text also includes here-doc bodies, which used to be
+omitted.
+.IP \(bu 4
+The UTF\-8 position cache is now reset when accessing magical variables, to
+avoid the string buffer and the UTF\-8 position cache getting out of sync
+[perl #114410].
+.IP \(bu 4
+Various cases of get magic being called twice for magical UTF\-8
+strings have been fixed.
+.IP \(bu 4
+This code (when not in the presence of \f(CW$&\fR etc)
+.Sp
+.Vb 2
+\&    $_ = \*(Aqx\*(Aq x 1_000_000;
+\&    1 while /(.)/;
+.Ve
+.Sp
+used to skip the buffer copy for performance reasons, but suffered from \f(CW$1\fR
+etc changing if the original string changed.  That's now been fixed.
+.IP \(bu 4
+Perl doesn't use PerlIO anymore to report out of memory messages, as PerlIO
+might attempt to allocate more memory.
+.IP \(bu 4
+In a regular expression, if something is quantified with \f(CW\*(C`{n,m}\*(C'\fR where
+\&\f(CW\*(C`n\ >\ m\*(C'\fR, it can't possibly match.  Previously this was a fatal
+error, but now is merely a warning (and that something won't match).
+[perl #82954].
+.IP \(bu 4
+It used to be possible for formats defined in subroutines that have
+subsequently been undefined and redefined to close over variables in the
+wrong pad (the newly-defined enclosing sub), resulting in crashes or
+"Bizarre copy" errors.
+.IP \(bu 4
+Redefinition of XSUBs at run time could produce warnings with the wrong
+line number.
+.IP \(bu 4
+The \f(CW%vd\fR sprintf format does not support version objects for alpha versions.
+It used to output the format itself (%vd) when passed an alpha version, and
+also emit an "Invalid conversion in printf" warning.  It no longer does,
+but produces the empty string in the output.  It also no longer leaks
+memory in this case.
+.IP \(bu 4
+\&\f(CW\*(C`$obj\->SUPER::method\*(C'\fR calls in the main package could fail if the
+SUPER package had already been accessed by other means.
+.IP \(bu 4
+Stash aliasing (\f(CW\*(C`*foo:: = *bar::\*(C'\fR) no longer causes SUPER calls to ignore
+changes to methods or \f(CW@ISA\fR or use the wrong package.
+.IP \(bu 4
+Method calls on packages whose names end in ::SUPER are no longer treated
+as SUPER method calls, resulting in failure to find the method.
+Furthermore, defining subroutines in such packages no longer causes them to
+be found by SUPER method calls on the containing package [perl #114924].
+.IP \(bu 4
+\&\f(CW\*(C`\ew\*(C'\fR now matches the code points U+200C (ZERO WIDTH NON-JOINER) and U+200D
+(ZERO WIDTH JOINER).  \f(CW\*(C`\eW\*(C'\fR no longer matches these.  This change is because
+Unicode corrected their definition of what \f(CW\*(C`\ew\*(C'\fR should match.
+.IP \(bu 4
+\&\f(CW\*(C`dump LABEL\*(C'\fR no longer leaks its label.
+.IP \(bu 4
+Constant folding no longer changes the behaviour of functions like \f(CWstat()\fR
+and \f(CWtruncate()\fR that can take either filenames or handles.
+\&\f(CW\*(C`stat 1 ? foo : bar\*(C'\fR nows treats its argument as a file name (since it is an
+arbitrary expression), rather than the handle "foo".
+.IP \(bu 4
+\&\f(CW\*(C`truncate FOO, $len\*(C'\fR no longer falls back to treating "FOO" as a file name if
+the filehandle has been deleted.  This was broken in Perl v5.16.0.
+.IP \(bu 4
+Subroutine redefinitions after sub-to-glob and glob-to-glob assignments no
+longer cause double frees or panic messages.
+.IP \(bu 4
+\&\f(CW\*(C`s///\*(C'\fR now turns vstrings into plain strings when performing a substitution,
+even if the resulting string is the same (\f(CW\*(C`s/a/a/\*(C'\fR).
+.IP \(bu 4
+Prototype mismatch warnings no longer erroneously treat constant subs as having
+no prototype when they actually have "".
+.IP \(bu 4
+Constant subroutines and forward declarations no longer prevent prototype
+mismatch warnings from omitting the sub name.
+.IP \(bu 4
+\&\f(CW\*(C`undef\*(C'\fR on a subroutine now clears call checkers.
+.IP \(bu 4
+The \f(CW\*(C`ref\*(C'\fR operator started leaking memory on blessed objects in Perl v5.16.0.
+This has been fixed [perl #114340].
+.IP \(bu 4
+\&\f(CW\*(C`use\*(C'\fR no longer tries to parse its arguments as a statement, making
+\&\f(CW\*(C`use constant { () };\*(C'\fR a syntax error [perl #114222].
+.IP \(bu 4
+On debugging builds, "uninitialized" warnings inside formats no longer cause
+assertion failures.
+.IP \(bu 4
+On debugging builds, subroutines nested inside formats no longer cause
+assertion failures [perl #78550].
+.IP \(bu 4
+Formats and \f(CW\*(C`use\*(C'\fR statements are now permitted inside formats.
+.IP \(bu 4
+\&\f(CW\*(C`print $x\*(C'\fR and \f(CW\*(C`sub { print $x }\->()\*(C'\fR now always produce the same output.
+It was possible for the latter to refuse to close over \f(CW$x\fR if the variable was
+not active; e.g., if it was defined outside a currently-running named
+subroutine.
+.IP \(bu 4
+Similarly, \f(CW\*(C`print $x\*(C'\fR and \f(CW\*(C`print eval \*(Aq$x\*(Aq\*(C'\fR now produce the same output.
+This also allows "my \f(CW$x\fR if 0" variables to be seen in the debugger [perl
+#114018].
+.IP \(bu 4
+Formats called recursively no longer stomp on their own lexical variables, but
+each recursive call has its own set of lexicals.
+.IP \(bu 4
+Attempting to free an active format or the handle associated with it no longer
+results in a crash.
+.IP \(bu 4
+Format parsing no longer gets confused by braces, semicolons and low-precedence
+operators.  It used to be possible to use braces as format delimiters (instead
+of \f(CW\*(C`=\*(C'\fR and \f(CW\*(C`.\*(C'\fR), but only sometimes.  Semicolons and low-precedence operators
+in format argument lines no longer confuse the parser into ignoring the line's
+return value.  In format argument lines, braces can now be used for anonymous
+hashes, instead of being treated always as \f(CW\*(C`do\*(C'\fR blocks.
+.IP \(bu 4
+Formats can now be nested inside code blocks in regular expressions and other
+quoted constructs (\f(CW\*(C`/(?{...})/\*(C'\fR and \f(CW\*(C`qq/${...}/\*(C'\fR) [perl #114040].
+.IP \(bu 4
+Formats are no longer created after compilation errors.
+.IP \(bu 4
+Under debugging builds, the \fB\-DA\fR command line option started crashing in Perl
+v5.16.0.  It has been fixed [perl #114368].
+.IP \(bu 4
+A potential deadlock scenario involving the premature termination of a pseudo\-
+forked child in a Windows build with ithreads enabled has been fixed.  This
+resolves the common problem of the \fIt/op/fork.t\fR test hanging on Windows [perl
+#88840].
+.IP \(bu 4
+The code which generates errors from \f(CWrequire()\fR could potentially read one or
+two bytes before the start of the filename for filenames less than three bytes
+long and ending \f(CW\*(C`/\e.p?\ez/\*(C'\fR.  This has now been fixed.  Note that it could
+never have happened with module names given to \f(CWuse()\fR or \f(CWrequire()\fR anyway.
+.IP \(bu 4
+The handling of pathnames of modules given to \f(CWrequire()\fR has been made
+thread-safe on VMS.
+.IP \(bu 4
+Non-blocking sockets have been fixed on VMS.
+.IP \(bu 4
+Pod can now be nested in code inside a quoted construct outside of a string
+eval.  This used to work only within string evals [perl #114040].
+.IP \(bu 4
+\&\f(CW\*(C`goto \*(Aq\*(Aq\*(C'\fR now looks for an empty label, producing the "goto must have
+label" error message, instead of exiting the program [perl #111794].
+.IP \(bu 4
+\&\f(CW\*(C`goto "\e0"\*(C'\fR now dies with "Can't find label" instead of "goto must have
+label".
+.IP \(bu 4
+The C function \f(CW\*(C`hv_store\*(C'\fR used to result in crashes when used on \f(CW\*(C`%^H\*(C'\fR
+[perl #111000].
+.IP \(bu 4
+A call checker attached to a closure prototype via \f(CW\*(C`cv_set_call_checker\*(C'\fR
+is now copied to closures cloned from it.  So \f(CW\*(C`cv_set_call_checker\*(C'\fR now
+works inside an attribute handler for a closure.
+.IP \(bu 4
+Writing to \f(CW$^N\fR used to have no effect.  Now it croaks with "Modification
+of a read-only value" by default, but that can be overridden by a custom
+regular expression engine, as with \f(CW$1\fR [perl #112184].
+.IP \(bu 4
+\&\f(CW\*(C`undef\*(C'\fR on a control character glob (\f(CW\*(C`undef *^H\*(C'\fR) no longer emits an
+erroneous warning about ambiguity [perl #112456].
+.IP \(bu 4
+For efficiency's sake, many operators and built-in functions return the
+same scalar each time.  Lvalue subroutines and subroutines in the CORE::
+namespace were allowing this implementation detail to leak through.
+\&\f(CW\*(C`print &CORE::uc("a"), &CORE::uc("b")\*(C'\fR used to print "BB".  The same thing
+would happen with an lvalue subroutine returning the return value of \f(CW\*(C`uc\*(C'\fR.
+Now the value is copied in such cases.
+.IP \(bu 4
+\&\f(CW\*(C`method {}\*(C'\fR syntax with an empty block or a block returning an empty list
+used to crash or use some random value left on the stack as its invocant.
+Now it produces an error.
+.IP \(bu 4
+\&\f(CW\*(C`vec\*(C'\fR now works with extremely large offsets (>2 GB) [perl #111730].
+.IP \(bu 4
+Changes to overload settings now take effect immediately, as do changes to
+inheritance that affect overloading.  They used to take effect only after
+\&\f(CW\*(C`bless\*(C'\fR.
+.Sp
+Objects that were created before a class had any overloading used to remain
+non-overloaded even if the class gained overloading through \f(CW\*(C`use overload\*(C'\fR
+or \f(CW@ISA\fR changes, and even after \f(CW\*(C`bless\*(C'\fR.  This has been fixed
+[perl #112708].
+.IP \(bu 4
+Classes with overloading can now inherit fallback values.
+.IP \(bu 4
+Overloading was not respecting a fallback value of 0 if there were
+overloaded objects on both sides of an assignment operator like \f(CW\*(C`+=\*(C'\fR
+[perl #111856].
+.IP \(bu 4
+\&\f(CW\*(C`pos\*(C'\fR now croaks with hash and array arguments, instead of producing
+erroneous warnings.
+.IP \(bu 4
+\&\f(CW\*(C`while(each %h)\*(C'\fR now implies \f(CW\*(C`while(defined($_ = each %h))\*(C'\fR, like
+\&\f(CW\*(C`readline\*(C'\fR and \f(CW\*(C`readdir\*(C'\fR.
+.IP \(bu 4
+Subs in the CORE:: namespace no longer crash after \f(CW\*(C`undef *_\*(C'\fR when called
+with no argument list (\f(CW&CORE::time\fR with no parentheses).
+.IP \(bu 4
+\&\f(CW\*(C`unpack\*(C'\fR no longer produces the "'/' must follow a numeric type in unpack"
+error when it is the data that are at fault [perl #60204].
+.IP \(bu 4
+\&\f(CW\*(C`join\*(C'\fR and \f(CW"@array"\fR now call FETCH only once on a tied \f(CW$"\fR
+[perl #8931].
+.IP \(bu 4
+Some subroutine calls generated by compiling core ops affected by a
+\&\f(CW\*(C`CORE::GLOBAL\*(C'\fR override had op checking performed twice.  The checking
+is always idempotent for pure Perl code, but the double checking can
+matter when custom call checkers are involved.
+.IP \(bu 4
+A race condition used to exist around fork that could cause a signal sent to
+the parent to be handled by both parent and child. Signals are now blocked
+briefly around fork to prevent this from happening [perl #82580].
+.IP \(bu 4
+The implementation of code blocks in regular expressions, such as \f(CW\*(C`(?{})\*(C'\fR
+and \f(CW\*(C`(??{})\*(C'\fR, has been heavily reworked to eliminate a whole slew of bugs.
+The main user-visible changes are:
+.RS 4
+.IP \(bu 4
+Code blocks within patterns are now parsed in the same pass as the
+surrounding code; in particular it is no longer necessary to have balanced
+braces: this now works:
+.Sp
+.Vb 1
+\&    /(?{  $x=\*(Aq{\*(Aq  })/
+.Ve
+.Sp
+This means that this error message is no longer generated:
+.Sp
+.Vb 1
+\&    Sequence (?{...}) not terminated or not {}\-balanced in regex
+.Ve
+.Sp
+but a new error may be seen:
+.Sp
+.Vb 1
+\&    Sequence (?{...}) not terminated with \*(Aq)\*(Aq
+.Ve
+.Sp
+In addition, literal code blocks within run-time patterns are only
+compiled once, at perl compile-time:
+.Sp
+.Vb 5
+\&    for my $p (...) {
+\&        # this \*(AqFOO\*(Aq block of code is compiled once,
+\&        # at the same time as the surrounding \*(Aqfor\*(Aq loop
+\&        /$p{(?{FOO;})/;
+\&    }
+.Ve
+.IP \(bu 4
+Lexical variables are now sane as regards scope, recursion and closure
+behavior. In particular, \f(CW\*(C`/A(?{B})C/\*(C'\fR behaves (from a closure viewpoint)
+exactly like \f(CW\*(C`/A/ && do { B } && /C/\*(C'\fR, while  \f(CW\*(C`qr/A(?{B})C/\*(C'\fR is like
+\&\f(CW\*(C`sub {/A/ && do { B } && /C/}\*(C'\fR. So this code now works how you might
+expect, creating three regexes that match 0, 1, and 2:
+.Sp
+.Vb 4
+\&    for my $i (0..2) {
+\&        push @r, qr/^(??{$i})$/;
+\&    }
+\&    "1" =~ $r[1]; # matches
+.Ve
+.IP \(bu 4
+The \f(CW\*(C`use re \*(Aqeval\*(Aq\*(C'\fR pragma is now only required for code blocks defined
+at runtime; in particular in the following, the text of the \f(CW$r\fR pattern is
+still interpolated into the new pattern and recompiled, but the individual
+compiled code-blocks within \f(CW$r\fR are reused rather than being recompiled,
+and \f(CW\*(C`use re \*(Aqeval\*(Aq\*(C'\fR isn't needed any more:
+.Sp
+.Vb 2
+\&    my $r = qr/abc(?{....})def/;
+\&    /xyz$r/;
+.Ve
+.IP \(bu 4
+Flow control operators no longer crash. Each code block runs in a new
+dynamic scope, so \f(CW\*(C`next\*(C'\fR etc. will not see
+any enclosing loops. \f(CW\*(C`return\*(C'\fR returns a value
+from the code block, not from any enclosing subroutine.
+.IP \(bu 4
+Perl normally caches the compilation of run-time patterns, and doesn't
+recompile if the pattern hasn't changed, but this is now disabled if
+required for the correct behavior of closures. For example:
+.Sp
+.Vb 5
+\&    my $code = \*(Aq(??{$x})\*(Aq;
+\&    for my $x (1..3) {
+\&        # recompile to see fresh value of $x each time
+\&        $x =~ /$code/;
+\&    }
+.Ve
+.IP \(bu 4
+The \f(CW\*(C`/msix\*(C'\fR and \f(CW\*(C`(?msix)\*(C'\fR etc. flags are now propagated into the return
+value from \f(CW\*(C`(??{})\*(C'\fR; this now works:
+.Sp
+.Vb 1
+\&    "AB" =~ /a(??{\*(Aqb\*(Aq})/i;
+.Ve
+.IP \(bu 4
+Warnings and errors will appear to come from the surrounding code (or for
+run-time code blocks, from an eval) rather than from an \f(CW\*(C`re_eval\*(C'\fR:
+.Sp
+.Vb 2
+\&    use re \*(Aqeval\*(Aq; $c = \*(Aq(?{ warn "foo" })\*(Aq; /$c/;
+\&    /(?{ warn "foo" })/;
+.Ve
+.Sp
+formerly gave:
+.Sp
+.Vb 2
+\&    foo at (re_eval 1) line 1.
+\&    foo at (re_eval 2) line 1.
+.Ve
+.Sp
+and now gives:
+.Sp
+.Vb 2
+\&    foo at (eval 1) line 1.
+\&    foo at /some/prog line 2.
+.Ve
+.RE
+.RS 4
+.RE
+.IP \(bu 4
+Perl now can be recompiled to use any Unicode version.  In v5.16, it
+worked on Unicodes 6.0 and 6.1, but there were various bugs if earlier
+releases were used; the older the release the more problems.
+.IP \(bu 4
+\&\f(CW\*(C`vec\*(C'\fR no longer produces "uninitialized" warnings in lvalue context
+[perl #9423].
+.IP \(bu 4
+An optimization involving fixed strings in regular expressions could cause
+a severe performance penalty in edge cases.  This has been fixed
+[perl #76546].
+.IP \(bu 4
+In certain cases, including empty subpatterns within a regular expression (such
+as \f(CW\*(C`(?:)\*(C'\fR or \f(CW\*(C`(?:|)\*(C'\fR) could disable some optimizations. This has been fixed.
+.IP \(bu 4
+The "Can't find an opnumber" message that \f(CW\*(C`prototype\*(C'\fR produces when passed
+a string like "CORE::nonexistent_keyword" now passes UTF\-8 and embedded
+NULs through unchanged [perl #97478].
+.IP \(bu 4
+\&\f(CW\*(C`prototype\*(C'\fR now treats magical variables like \f(CW$1\fR the same way as
+non-magical variables when checking for the CORE:: prefix, instead of
+treating them as subroutine names.
+.IP \(bu 4
+Under threaded perls, a runtime code block in a regular expression could
+corrupt the package name stored in the op tree, resulting in bad reads
+in \f(CW\*(C`caller\*(C'\fR, and possibly crashes [perl #113060].
+.IP \(bu 4
+Referencing a closure prototype (\f(CW\*(C`\e&{$_[1]}\*(C'\fR in an attribute handler for a
+closure) no longer results in a copy of the subroutine (or assertion
+failures on debugging builds).
+.IP \(bu 4
+\&\f(CW\*(C`eval \*(Aq_\|_PACKAGE_\|_\*(Aq\*(C'\fR now returns the right answer on threaded builds if
+the current package has been assigned over (as in
+\&\f(CW\*(C`*ThisPackage:: = *ThatPackage::\*(C'\fR) [perl #78742].
+.IP \(bu 4
+If a package is deleted by code that it calls, it is possible for \f(CW\*(C`caller\*(C'\fR
+to see a stack frame belonging to that deleted package.  \f(CW\*(C`caller\*(C'\fR could
+crash if the stash's memory address was reused for a scalar and a
+substitution was performed on the same scalar [perl #113486].
+.IP \(bu 4
+\&\f(CW\*(C`UNIVERSAL::can\*(C'\fR no longer treats its first argument differently
+depending on whether it is a string or number internally.
+.IP \(bu 4
+\&\f(CW\*(C`open\*(C'\fR with \f(CW\*(C`<&\*(C'\fR for the mode checks to see whether the third argument is
+a number, in determining whether to treat it as a file descriptor or a handle
+name.  Magical variables like \f(CW$1\fR were always failing the numeric check and
+being treated as handle names.
+.IP \(bu 4
+\&\f(CW\*(C`warn\*(C'\fR's handling of magical variables (\f(CW$1\fR, ties) has undergone several
+fixes.  \f(CW\*(C`FETCH\*(C'\fR is only called once now on a tied argument or a tied \f(CW$@\fR
+[perl #97480].  Tied variables returning objects that stringify as "" are
+no longer ignored.  A tied \f(CW$@\fR that happened to return a reference the
+\&\fIprevious\fR time it was used is no longer ignored.
+.IP \(bu 4
+\&\f(CW\*(C`warn ""\*(C'\fR now treats \f(CW$@\fR with a number in it the same way, regardless of
+whether it happened via \f(CW\*(C`$@=3\*(C'\fR or \f(CW\*(C`$@="3"\*(C'\fR.  It used to ignore the
+former.  Now it appends "\et...caught", as it has always done with
+\&\f(CW\*(C`$@="3"\*(C'\fR.
+.IP \(bu 4
+Numeric operators on magical variables (e.g., \f(CW\*(C`$1\ +\ 1\*(C'\fR) used to use
+floating point operations even where integer operations were more appropriate,
+resulting in loss of accuracy on 64\-bit platforms [perl #109542].
+.IP \(bu 4
+Unary negation no longer treats a string as a number if the string happened
+to be used as a number at some point.  So, if \f(CW$x\fR contains the string "dogs",
+\&\f(CW\*(C`\-$x\*(C'\fR returns "\-dogs" even if \f(CW\*(C`$y=0+$x\*(C'\fR has happened at some point.
+.IP \(bu 4
+In Perl v5.14, \f(CW\*(C`\-\*(Aq\-10\*(Aq\*(C'\fR was fixed to return "10", not "+10".  But magical
+variables (\f(CW$1\fR, ties) were not fixed till now [perl #57706].
+.IP \(bu 4
+Unary negation now treats strings consistently, regardless of the internal
+\&\f(CW\*(C`UTF8\*(C'\fR flag.
+.IP \(bu 4
+A regression introduced in Perl v5.16.0 involving
+\&\f(CW\*(C`tr/\fR\f(CISEARCHLIST\fR\f(CW/\fR\f(CIREPLACEMENTLIST\fR\f(CW/\*(C'\fR has been fixed.  Only the first
+instance is supposed to be meaningful if a character appears more than
+once in \f(CW\*(C`\fR\f(CISEARCHLIST\fR\f(CW\*(C'\fR.  Under some circumstances, the final instance
+was overriding all earlier ones.  [perl #113584]
+.IP \(bu 4
+Regular expressions like \f(CW\*(C`qr/\e87/\*(C'\fR previously silently inserted a NUL
+character, thus matching as if it had been written \f(CW\*(C`qr/\e00087/\*(C'\fR.  Now it
+matches as if it had been written as \f(CW\*(C`qr/87/\*(C'\fR, with a message that the
+sequence \f(CW"\e8"\fR is unrecognized.
+.IP \(bu 4
+\&\f(CW\*(C`_\|_SUB_\|_\*(C'\fR now works in special blocks (\f(CW\*(C`BEGIN\*(C'\fR, \f(CW\*(C`END\*(C'\fR, etc.).
+.IP \(bu 4
+Thread creation on Windows could theoretically result in a crash if done
+inside a \f(CW\*(C`BEGIN\*(C'\fR block.  It still does not work properly, but it no longer
+crashes [perl #111610].
+.IP \(bu 4
+\&\f(CW\*(C`\e&{\*(Aq\*(Aq}\*(C'\fR (with the empty string) now autovivifies a stub like any other
+sub name, and no longer produces the "Unable to create sub" error
+[perl #94476].
+.IP \(bu 4
+A regression introduced in v5.14.0 has been fixed, in which some calls
+to the \f(CW\*(C`re\*(C'\fR module would clobber \f(CW$_\fR [perl #113750].
+.IP \(bu 4
+\&\f(CW\*(C`do FILE\*(C'\fR now always either sets or clears \f(CW$@\fR, even when the file can't be
+read. This ensures that testing \f(CW$@\fR first (as recommended by the
+documentation) always returns the correct result.
+.IP \(bu 4
+The array iterator used for the \f(CW\*(C`each @array\*(C'\fR construct is now correctly
+reset when \f(CW@array\fR is cleared [perl #75596]. This happens, for example, when
+the array is globally assigned to, as in \f(CW\*(C`@array = (...)\*(C'\fR, but not when its
+\&\fBvalues\fR are assigned to. In terms of the XS API, it means that \f(CWav_clear()\fR
+will now reset the iterator.
+.Sp
+This mirrors the behaviour of the hash iterator when the hash is cleared.
+.IP \(bu 4
+\&\f(CW\*(C`$class\->can\*(C'\fR, \f(CW\*(C`$class\->isa\*(C'\fR, and \f(CW\*(C`$class\->DOES\*(C'\fR now return
+correct results, regardless of whether that package referred to by \f(CW$class\fR
+exists [perl #47113].
+.IP \(bu 4
+Arriving signals no longer clear \f(CW$@\fR [perl #45173].
+.IP \(bu 4
+Allow \f(CW\*(C`my ()\*(C'\fR declarations with an empty variable list [perl #113554].
+.IP \(bu 4
+During parsing, subs declared after errors no longer leave stubs
+[perl #113712].
+.IP \(bu 4
+Closures containing no string evals no longer hang on to their containing
+subroutines, allowing variables closed over by outer subroutines to be
+freed when the outer sub is freed, even if the inner sub still exists
+[perl #89544].
+.IP \(bu 4
+Duplication of in-memory filehandles by opening with a "<&=" or ">&=" mode
+stopped working properly in v5.16.0.  It was causing the new handle to
+reference a different scalar variable.  This has been fixed [perl #113764].
+.IP \(bu 4
+\&\f(CW\*(C`qr//\*(C'\fR expressions no longer crash with custom regular expression engines
+that do not set \f(CW\*(C`offs\*(C'\fR at regular expression compilation time
+[perl #112962].
+.IP \(bu 4
+\&\f(CW\*(C`delete local\*(C'\fR no longer crashes with certain magical arrays and hashes
+[perl #112966].
+.IP \(bu 4
+\&\f(CW\*(C`local\*(C'\fR on elements of certain magical arrays and hashes used not to
+arrange to have the element deleted on scope exit, even if the element did
+not exist before \f(CW\*(C`local\*(C'\fR.
+.IP \(bu 4
+\&\f(CWscalar(write)\fR no longer returns multiple items [perl #73690].
+.IP \(bu 4
+String to floating point conversions no longer misparse certain strings under
+\&\f(CW\*(C`use locale\*(C'\fR [perl #109318].
+.IP \(bu 4
+\&\f(CW@INC\fR filters that die no longer leak memory [perl #92252].
+.IP \(bu 4
+The implementations of overloaded operations are now called in the correct
+context. This allows, among other things, being able to properly override
+\&\f(CW\*(C`<>\*(C'\fR [perl #47119].
+.IP \(bu 4
+Specifying only the \f(CW\*(C`fallback\*(C'\fR key when calling \f(CW\*(C`use overload\*(C'\fR now behaves
+properly [perl #113010].
+.IP \(bu 4
+\&\f(CW\*(C`sub foo { my $a = 0; while ($a) { ... } }\*(C'\fR and
+\&\f(CW\*(C`sub foo { while (0) { ... } }\*(C'\fR now return the same thing [perl #73618].
+.IP \(bu 4
+String negation now behaves the same under \f(CW\*(C`use integer;\*(C'\fR as it does
+without [perl #113012].
+.IP \(bu 4
+\&\f(CW\*(C`chr\*(C'\fR now returns the Unicode replacement character (U+FFFD) for \-1,
+regardless of the internal representation.  \-1 used to wrap if the argument
+was tied or a string internally.
+.IP \(bu 4
+Using a \f(CW\*(C`format\*(C'\fR after its enclosing sub was freed could crash as of
+perl v5.12.0, if the format referenced lexical variables from the outer sub.
+.IP \(bu 4
+Using a \f(CW\*(C`format\*(C'\fR after its enclosing sub was undefined could crash as of
+perl v5.10.0, if the format referenced lexical variables from the outer sub.
+.IP \(bu 4
+Using a \f(CW\*(C`format\*(C'\fR defined inside a closure, which format references
+lexical variables from outside, never really worked unless the \f(CW\*(C`write\*(C'\fR
+call was directly inside the closure.  In v5.10.0 it even started crashing.
+Now the copy of that closure nearest the top of the call stack is used to
+find those variables.
+.IP \(bu 4
+Formats that close over variables in special blocks no longer crash if a
+stub exists with the same name as the special block before the special
+block is compiled.
+.IP \(bu 4
+The parser no longer gets confused, treating \f(CW\*(C`eval foo ()\*(C'\fR as a syntax
+error if preceded by \f(CW\*(C`print;\*(C'\fR [perl #16249].
+.IP \(bu 4
+The return value of \f(CW\*(C`syscall\*(C'\fR is no longer truncated on 64\-bit platforms
+[perl #113980].
+.IP \(bu 4
+Constant folding no longer causes \f(CW\*(C`print 1 ? FOO : BAR\*(C'\fR to print to the
+FOO handle [perl #78064].
+.IP \(bu 4
+\&\f(CW\*(C`do subname\*(C'\fR now calls the named subroutine and uses the file name it
+returns, instead of opening a file named "subname".
+.IP \(bu 4
+Subroutines looked up by rv2cv check hooks (registered by XS modules) are
+now taken into consideration when determining whether \f(CW\*(C`foo bar\*(C'\fR should be
+the sub call \f(CWfoo(bar)\fR or the method call \f(CW\*(C`"bar"\->foo\*(C'\fR.
+.IP \(bu 4
+\&\f(CW\*(C`CORE::foo::bar\*(C'\fR is no longer treated specially, allowing global overrides
+to be called directly via \f(CWCORE::GLOBAL::uc(...)\fR [perl #113016].
+.IP \(bu 4
+Calling an undefined sub whose typeglob has been undefined now produces the
+customary "Undefined subroutine called" error, instead of "Not a CODE
+reference".
+.IP \(bu 4
+Two bugs involving \f(CW@ISA\fR have been fixed.  \f(CW\*(C`*ISA = *glob_without_array\*(C'\fR and
+\&\f(CW\*(C`undef *ISA; @{*ISA}\*(C'\fR would prevent future modifications to \f(CW@ISA\fR from
+updating the internal caches used to look up methods.  The
+*glob_without_array case was a regression from Perl v5.12.
+.IP \(bu 4
+Regular expression optimisations sometimes caused \f(CW\*(C`$\*(C'\fR with \f(CW\*(C`/m\*(C'\fR to
+produce failed or incorrect matches [perl #114068].
+.IP \(bu 4
+\&\f(CW\*(C`_\|_SUB_\|_\*(C'\fR now works in a \f(CW\*(C`sort\*(C'\fR block when the enclosing subroutine is
+predeclared with \f(CW\*(C`sub foo;\*(C'\fR syntax [perl #113710].
+.IP \(bu 4
+Unicode properties only apply to Unicode code points, which leads to
+some subtleties when regular expressions are matched against
+above-Unicode code points.  There is a warning generated to draw your
+attention to this.  However, this warning was being generated
+inappropriately in some cases, such as when a program was being parsed.
+Non-Unicode matches such as \f(CW\*(C`\ew\*(C'\fR and \f(CW\*(C`[:word:]\*(C'\fR should not generate the
+warning, as their definitions don't limit them to apply to only Unicode
+code points.  Now the message is only generated when matching against
+\&\f(CW\*(C`\ep{}\*(C'\fR and \f(CW\*(C`\eP{}\*(C'\fR.  There remains a bug, [perl #114148], for the very
+few properties in Unicode that match just a single code point.  The
+warning is not generated if they are matched against an above-Unicode
+code point.
+.IP \(bu 4
+Uninitialized warnings mentioning hash elements would only mention the
+element name if it was not in the first bucket of the hash, due to an
+off-by-one error.
+.IP \(bu 4
+A regular expression optimizer bug could cause multiline "^" to behave
+incorrectly in the presence of line breaks, such that
+\&\f(CW\*(C`"/\en\en" =~ m#\eA(?:^/$)#im\*(C'\fR would not match [perl #115242].
+.IP \(bu 4
+Failed \f(CW\*(C`fork\*(C'\fR in list context no longer corrupts the stack.
+\&\f(CW\*(C`@a = (1, 2, fork, 3)\*(C'\fR used to gobble up the 2 and assign \f(CW\*(C`(1, undef, 3)\*(C'\fR
+if the \f(CW\*(C`fork\*(C'\fR call failed.
+.IP \(bu 4
+Numerous memory leaks have been fixed, mostly involving tied variables that
+die, regular expression character classes and code blocks, and syntax
+errors.
+.IP \(bu 4
+Assigning a regular expression (\f(CW\*(C`${qr//}\*(C'\fR) to a variable that happens to
+hold a floating point number no longer causes assertion failures on
+debugging builds.
+.IP \(bu 4
+Assigning a regular expression to a scalar containing a number no longer
+causes subsequent numification to produce random numbers.
+.IP \(bu 4
+Assigning a regular expression to a magic variable no longer wipes away the
+magic.  This was a regression from v5.10.
+.IP \(bu 4
+Assigning a regular expression to a blessed scalar no longer results in
+crashes.  This was also a regression from v5.10.
+.IP \(bu 4
+Regular expression can now be assigned to tied hash and array elements with
+flattening into strings.
+.IP \(bu 4
+Numifying a regular expression no longer results in an uninitialized
+warning.
+.IP \(bu 4
+Negative array indices no longer cause EXISTS methods of tied variables to
+be ignored.  This was a regression from v5.12.
+.IP \(bu 4
+Negative array indices no longer result in crashes on arrays tied to
+non-objects.
+.IP \(bu 4
+\&\f(CW\*(C`$byte_overload .= $utf8\*(C'\fR no longer results in doubly-encoded UTF\-8 if the
+left-hand scalar happened to have produced a UTF\-8 string the last time
+overloading was invoked.
+.IP \(bu 4
+\&\f(CW\*(C`goto &sub\*(C'\fR now uses the current value of \f(CW@_\fR, instead of using the array
+the subroutine was originally called with.  This means
+\&\f(CW\*(C`local @_ = (...); goto &sub\*(C'\fR now works [perl #43077].
+.IP \(bu 4
+If a debugger is invoked recursively, it no longer stomps on its own
+lexical variables.  Formerly under recursion all calls would share the same
+set of lexical variables [perl #115742].
+.IP \(bu 4
+\&\f(CW*_{ARRAY}\fR returned from a subroutine no longer spontaneously
+becomes empty.
+.IP \(bu 4
+When using \f(CW\*(C`say\*(C'\fR to print to a tied filehandle, the value of \f(CW\*(C`$\e\*(C'\fR is
+correctly localized, even if it was previously undef.  [perl #119927]
+.SH "Known Problems"
+.IX Header "Known Problems"
+.IP \(bu 4
+UTF8\-flagged strings in \f(CW%ENV\fR on HP-UX 11.00 are buggy
+.Sp
+The interaction of UTF8\-flagged strings and \f(CW%ENV\fR on HP-UX 11.00 is
+currently dodgy in some not-yet-fully-diagnosed way.  Expect test
+failures in \fIt/op/magic.t\fR, followed by unknown behavior when storing
+wide characters in the environment.
+.SH Obituary
+.IX Header "Obituary"
+Hojung Yoon (AMORETTE), 24, of Seoul, South Korea, went to his long rest
+on May 8, 2013 with llama figurine and autographed TIMTOADY card.  He
+was a brilliant young Perl 5 & 6 hacker and a devoted member of
+Seoul.pm.  He programmed Perl, talked Perl, ate Perl, and loved Perl.  We
+believe that he is still programming in Perl with his broken IBM laptop
+somewhere.  He will be missed.
+.SH Acknowledgements
+.IX Header "Acknowledgements"
+Perl v5.18.0 represents approximately 12 months of development since
+Perl v5.16.0 and contains approximately 400,000 lines of changes across
+2,100 files from 113 authors.
+.PP
+Perl continues to flourish into its third decade thanks to a vibrant
+community of users and developers. The following people are known to
+have contributed the improvements that became Perl v5.18.0:
+.PP
+Aaron Crane, Aaron Trevena, Abhijit Menon-Sen, Adrian M. Enache, Alan
+Haggai Alavi, Alexandr Ciornii, Andrew Tam, Andy Dougherty, Anton Nikishaev,
+Aristotle Pagaltzis, Augustina Blair, Bob Ernst, Brad Gilbert, Breno G. de
+Oliveira, Brian Carlson, Brian Fraser, Charlie Gonzalez, Chip Salzenberg, Chris
+\&'BinGOs' Williams, Christian Hansen, Colin Kuskie, Craig A. Berry, Dagfinn
+Ilmari Mannsåker, Daniel Dragan, Daniel Perrett, Darin McBride, Dave Rolsky,
+David Golden, David Leadbeater, David Mitchell, David Nicol, Dominic
+Hargreaves, E. Choroba, Eric Brine, Evan Miller, Father Chrysostomos, Florian
+Ragwitz, François Perrad, George Greer, Goro Fuji, H.Merijn Brand, Herbert
+Breunung, Hugo van der Sanden, Igor Zaytsev, James E Keenan, Jan Dubois,
+Jasmine Ahuja, Jerry D. Hedden, Jess Robinson, Jesse Luehrs, Joaquin Ferrero,
+Joel Berger, John Goodyear, John Peacock, Karen Etheridge, Karl Williamson,
+Karthik Rajagopalan, Kent Fredric, Leon Timmermans, Lucas Holt, Lukas Mai,
+Marcus Holland-Moritz, Markus Jansen, Martin Hasch, Matthew Horsfall, Max
+Maischein, Michael G Schwern, Michael Schroeder, Moritz Lenz, Nicholas Clark,
+Niko Tyni, Oleg Nesterov, Patrik Hägglund, Paul Green, Paul Johnson, Paul
+Marquess, Peter Martini, Rafael Garcia-Suarez, Reini Urban, Renee Baecker,
+Rhesa Rozendaal, Ricardo Signes, Robin Barker, Ronald J. Kimball, Ruslan
+Zakirov, Salvador Fandiño, Sawyer X, Scott Lanning, Sergey Alekseev, Shawn M
+Moore, Shirakata Kentaro, Shlomi Fish, Sisyphus, Smylers, Steffen Müller,
+Steve Hay, Steve Peters, Steven Schubiger, Sullivan Beck, Sven Strickroth,
+Sébastien Aperghis-Tramoni, Thomas Sibley, Tobias Leich, Tom Wyant, Tony Cook,
+Vadim Konovalov, Vincent Pit, Volker Schatz, Walt Mankowski, Yves Orton,
+Zefram.
+.PP
+The list above is almost certainly incomplete as it is automatically generated
+from version control history. In particular, it does not include the names of
+the (very much appreciated) contributors who reported issues to the Perl bug
+tracker.
+.PP
+Many of the changes included in this version originated in the CPAN modules
+included in Perl's core. We're grateful to the entire CPAN community for
+helping Perl to flourish.
+.PP
+For a more complete list of all of Perl's historical contributors, please see
+the \fIAUTHORS\fR file in the Perl source distribution.
+.SH "Reporting Bugs"
+.IX Header "Reporting Bugs"
+If you find what you think is a bug, you might check the articles recently
+posted to the comp.lang.perl.misc newsgroup and the perl bug database at
+http://rt.perl.org/perlbug/ .  There may also be information at
+http://www.perl.org/ , the Perl Home Page.
+.PP
+If you believe you have an unreported bug, please run the perlbug program
+included with your release.  Be sure to trim your bug down to a tiny but
+sufficient test case.  Your bug report, along with the output of \f(CW\*(C`perl \-V\*(C'\fR,
+will be sent off to perlbug@perl.org to be analysed by the Perl porting team.
+.PP
+If the bug you are reporting has security implications, which make it
+inappropriate to send to a publicly archived mailing list, then please send it
+to perl5\-security\-report@perl.org.  This points to a closed subscription
+unarchived mailing list, which includes all the core committers, who will be
+able to help assess the impact of issues, figure out a resolution, and help
+co-ordinate the release of patches to mitigate or fix the problem across all
+platforms on which Perl is supported.  Please only use this address for
+security issues in the Perl core, not for modules independently distributed on
+CPAN.
+.SH "SEE ALSO"
+.IX Header "SEE ALSO"
+The \fIChanges\fR file for an explanation of how to view exhaustive details on
+what changed.
+.PP
+The \fIINSTALL\fR file for how to build Perl.
+.PP
+The \fIREADME\fR file for general stuff.
+.PP
+The \fIArtistic\fR and \fICopying\fR files for copyright information.