Adding upstream version 4.22.0.upstream/4.22.0

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

1 files changed, 2870 insertions, 0 deletions

diff --git a/upstream/fedora-40/man1/perl56delta.1 b/upstream/fedora-40/man1/perl56delta.1
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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 "PERL56DELTA 1"
+.TH PERL56DELTA 1 2024-01-25 "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
+perl56delta \- what's new for perl v5.6.0
+.SH DESCRIPTION
+.IX Header "DESCRIPTION"
+This document describes differences between the 5.005 release and the 5.6.0
+release.
+.SH "Core Enhancements"
+.IX Header "Core Enhancements"
+.SS "Interpreter cloning, threads, and concurrency"
+.IX Subsection "Interpreter cloning, threads, and concurrency"
+Perl 5.6.0 introduces the beginnings of support for running multiple
+interpreters concurrently in different threads.  In conjunction with
+the \fBperl_clone()\fR API call, which can be used to selectively duplicate
+the state of any given interpreter, it is possible to compile a
+piece of code once in an interpreter, clone that interpreter
+one or more times, and run all the resulting interpreters in distinct
+threads.
+.PP
+On the Windows platform, this feature is used to emulate \fBfork()\fR at the
+interpreter level.  See perlfork for details about that.
+.PP
+This feature is still in evolution.  It is eventually meant to be used
+to selectively clone a subroutine and data reachable from that
+subroutine in a separate interpreter and run the cloned subroutine
+in a separate thread.  Since there is no shared data between the
+interpreters, little or no locking will be needed (unless parts of
+the symbol table are explicitly shared).  This is obviously intended
+to be an easy-to-use replacement for the existing threads support.
+.PP
+Support for cloning interpreters and interpreter concurrency can be
+enabled using the \-Dusethreads Configure option (see win32/Makefile for
+how to enable it on Windows.)  The resulting perl executable will be
+functionally identical to one that was built with \-Dmultiplicity, but
+the \fBperl_clone()\fR API call will only be available in the former.
+.PP
+\&\-Dusethreads enables the cpp macro USE_ITHREADS by default, which in turn
+enables Perl source code changes that provide a clear separation between
+the op tree and the data it operates with.  The former is immutable, and
+can therefore be shared between an interpreter and all of its clones,
+while the latter is considered local to each interpreter, and is therefore
+copied for each clone.
+.PP
+Note that building Perl with the \-Dusemultiplicity Configure option
+is adequate if you wish to run multiple \fBindependent\fR interpreters
+concurrently in different threads.  \-Dusethreads only provides the
+additional functionality of the \fBperl_clone()\fR API call and other
+support for running \fBcloned\fR interpreters concurrently.
+.PP
+.Vb 2
+\&    NOTE: This is an experimental feature.  Implementation details are
+\&    subject to change.
+.Ve
+.SS "Lexically scoped warning categories"
+.IX Subsection "Lexically scoped warning categories"
+You can now control the granularity of warnings emitted by perl at a finer
+level using the \f(CW\*(C`use warnings\*(C'\fR pragma.  warnings and perllexwarn
+have copious documentation on this feature.
+.SS "Unicode and UTF\-8 support"
+.IX Subsection "Unicode and UTF-8 support"
+Perl now uses UTF\-8 as its internal representation for character
+strings.  The \f(CW\*(C`utf8\*(C'\fR and \f(CW\*(C`bytes\*(C'\fR pragmas are used to control this support
+in the current lexical scope.  See perlunicode, utf8 and bytes for
+more information.
+.PP
+This feature is expected to evolve quickly to support some form of I/O
+disciplines that can be used to specify the kind of input and output data
+(bytes or characters).  Until that happens, additional modules from CPAN
+will be needed to complete the toolkit for dealing with Unicode.
+.PP
+.Vb 2
+\&    NOTE: This should be considered an experimental feature.  Implementation
+\&    details are subject to change.
+.Ve
+.SS "Support for interpolating named characters"
+.IX Subsection "Support for interpolating named characters"
+The new \f(CW\*(C`\eN\*(C'\fR escape interpolates named characters within strings.
+For example, \f(CW"Hi! \eN{WHITE SMILING FACE}"\fR evaluates to a string
+with a unicode smiley face at the end.
+.SS """our"" declarations"
+.IX Subsection """our"" declarations"
+An "our" declaration introduces a value that can be best understood
+as a lexically scoped symbolic alias to a global variable in the
+package that was current where the variable was declared.  This is
+mostly useful as an alternative to the \f(CW\*(C`vars\*(C'\fR pragma, but also provides
+the opportunity to introduce typing and other attributes for such
+variables.  See "our" in perlfunc.
+.SS "Support for strings represented as a vector of ordinals"
+.IX Subsection "Support for strings represented as a vector of ordinals"
+Literals of the form \f(CW\*(C`v1.2.3.4\*(C'\fR are now parsed as a string composed
+of characters with the specified ordinals.  This is an alternative, more
+readable way to construct (possibly unicode) strings instead of
+interpolating characters, as in \f(CW"\ex{1}\ex{2}\ex{3}\ex{4}"\fR.  The leading
+\&\f(CW\*(C`v\*(C'\fR may be omitted if there are more than two ordinals, so \f(CW1.2.3\fR is
+parsed the same as \f(CW\*(C`v1.2.3\*(C'\fR.
+.PP
+Strings written in this form are also useful to represent version "numbers".
+It is easy to compare such version "numbers" (which are really just plain
+strings) using any of the usual string comparison operators \f(CW\*(C`eq\*(C'\fR, \f(CW\*(C`ne\*(C'\fR,
+\&\f(CW\*(C`lt\*(C'\fR, \f(CW\*(C`gt\*(C'\fR, etc., or perform bitwise string operations on them using \f(CW\*(C`|\*(C'\fR,
+\&\f(CW\*(C`&\*(C'\fR, etc.
+.PP
+In conjunction with the new \f(CW$^V\fR magic variable (which contains
+the perl version as a string), such literals can be used as a readable way
+to check if you're running a particular version of Perl:
+.PP
+.Vb 4
+\&    # this will parse in older versions of Perl also
+\&    if ($^V and $^V gt v5.6.0) {
+\&        # new features supported
+\&    }
+.Ve
+.PP
+\&\f(CW\*(C`require\*(C'\fR and \f(CW\*(C`use\*(C'\fR also have some special magic to support such
+literals, but this particular usage should be avoided because it leads to
+misleading error messages under versions of Perl which don't support vector
+strings.  Using a true version number will ensure correct behavior in all
+versions of Perl:
+.PP
+.Vb 2
+\&    require 5.006;    # run time check for v5.6
+\&    use 5.006_001;    # compile time check for v5.6.1
+.Ve
+.PP
+Also, \f(CW\*(C`sprintf\*(C'\fR and \f(CW\*(C`printf\*(C'\fR support the Perl-specific format flag \f(CW%v\fR
+to print ordinals of characters in arbitrary strings:
+.PP
+.Vb 3
+\&    printf "v%vd", $^V;         # prints current version, such as "v5.5.650"
+\&    printf "%*vX", ":", $addr;  # formats IPv6 address
+\&    printf "%*vb", " ", $bits;  # displays bitstring
+.Ve
+.PP
+See "Scalar value constructors" in perldata for additional information.
+.SS "Improved Perl version numbering system"
+.IX Subsection "Improved Perl version numbering system"
+Beginning with Perl version 5.6.0, the version number convention has been
+changed to a "dotted integer" scheme that is more commonly found in open
+source projects.
+.PP
+Maintenance versions of v5.6.0 will be released as v5.6.1, v5.6.2 etc.
+The next development series following v5.6.0 will be numbered v5.7.x,
+beginning with v5.7.0, and the next major production release following
+v5.6.0 will be v5.8.0.
+.PP
+The English module now sets \f(CW$PERL_VERSION\fR to $^V (a string value) rather
+than \f(CW$]\fR (a numeric value).  (This is a potential incompatibility.
+Send us a report via perlbug if you are affected by this.)
+.PP
+The v1.2.3 syntax is also now legal in Perl.
+See "Support for strings represented as a vector of ordinals" for more on that.
+.PP
+To cope with the new versioning system's use of at least three significant
+digits for each version component, the method used for incrementing the
+subversion number has also changed slightly.  We assume that versions older
+than v5.6.0 have been incrementing the subversion component in multiples of
+10.  Versions after v5.6.0 will increment them by 1.  Thus, using the new
+notation, 5.005_03 is the "same" as v5.5.30, and the first maintenance
+version following v5.6.0 will be v5.6.1 (which should be read as being
+equivalent to a floating point value of 5.006_001 in the older format,
+stored in \f(CW$]\fR).
+.SS "New syntax for declaring subroutine attributes"
+.IX Subsection "New syntax for declaring subroutine attributes"
+Formerly, if you wanted to mark a subroutine as being a method call or
+as requiring an automatic \fBlock()\fR when it is entered, you had to declare
+that with a \f(CW\*(C`use attrs\*(C'\fR pragma in the body of the subroutine.
+That can now be accomplished with declaration syntax, like this:
+.PP
+.Vb 5
+\&    sub mymethod : locked method;
+\&    ...
+\&    sub mymethod : locked method {
+\&        ...
+\&    }
+\&
+\&    sub othermethod :locked :method;
+\&    ...
+\&    sub othermethod :locked :method {
+\&        ...
+\&    }
+.Ve
+.PP
+(Note how only the first \f(CW\*(C`:\*(C'\fR is mandatory, and whitespace surrounding
+the \f(CW\*(C`:\*(C'\fR is optional.)
+.PP
+\&\fIAutoSplit.pm\fR and \fISelfLoader.pm\fR have been updated to keep the attributes
+with the stubs they provide.  See attributes.
+.SS "File and directory handles can be autovivified"
+.IX Subsection "File and directory handles can be autovivified"
+Similar to how constructs such as \f(CW\*(C`$x\->[0]\*(C'\fR autovivify a reference,
+handle constructors (\fBopen()\fR, \fBopendir()\fR, \fBpipe()\fR, \fBsocketpair()\fR, \fBsysopen()\fR,
+\&\fBsocket()\fR, and \fBaccept()\fR) now autovivify a file or directory handle
+if the handle passed to them is an uninitialized scalar variable.  This
+allows the constructs such as \f(CW\*(C`open(my $fh, ...)\*(C'\fR and \f(CW\*(C`open(local $fh,...)\*(C'\fR
+to be used to create filehandles that will conveniently be closed
+automatically when the scope ends, provided there are no other references
+to them.  This largely eliminates the need for typeglobs when opening
+filehandles that must be passed around, as in the following example:
+.PP
+.Vb 5
+\&    sub myopen {
+\&        open my $fh, "@_"
+\&             or die "Can\*(Aqt open \*(Aq@_\*(Aq: $!";
+\&        return $fh;
+\&    }
+\&
+\&    {
+\&        my $f = myopen("</etc/motd");
+\&        print <$f>;
+\&        # $f implicitly closed here
+\&    }
+.Ve
+.SS "\fBopen()\fP with more than two arguments"
+.IX Subsection "open() with more than two arguments"
+If \fBopen()\fR is passed three arguments instead of two, the second argument
+is used as the mode and the third argument is taken to be the file name.
+This is primarily useful for protecting against unintended magic behavior
+of the traditional two-argument form.  See "open" in perlfunc.
+.SS "64\-bit support"
+.IX Subsection "64-bit support"
+Any platform that has 64\-bit integers either
+.PP
+.Vb 3
+\&        (1) natively as longs or ints
+\&        (2) via special compiler flags
+\&        (3) using long long or int64_t
+.Ve
+.PP
+is able to use "quads" (64\-bit integers) as follows:
+.IP \(bu 4
+constants (decimal, hexadecimal, octal, binary) in the code
+.IP \(bu 4
+arguments to \fBoct()\fR and \fBhex()\fR
+.IP \(bu 4
+arguments to \fBprint()\fR, \fBprintf()\fR and \fBsprintf()\fR (flag prefixes ll, L, q)
+.IP \(bu 4
+printed as such
+.IP \(bu 4
+\&\fBpack()\fR and \fBunpack()\fR "q" and "Q" formats
+.IP \(bu 4
+in basic arithmetics: + \- * / % (NOTE: operating close to the limits
+of the integer values may produce surprising results)
+.IP \(bu 4
+in bit arithmetics: & | ^ ~ << >> (NOTE: these used to be forced 
+to be 32 bits wide but now operate on the full native width.)
+.IP \(bu 4
+\&\fBvec()\fR
+.PP
+Note that unless you have the case (a) you will have to configure
+and compile Perl using the \-Duse64bitint Configure flag.
+.PP
+.Vb 2
+\&    NOTE: The Configure flags \-Duselonglong and \-Duse64bits have been
+\&    deprecated.  Use \-Duse64bitint instead.
+.Ve
+.PP
+There are actually two modes of 64\-bitness: the first one is achieved
+using Configure \-Duse64bitint and the second one using Configure
+\&\-Duse64bitall.  The difference is that the first one is minimal and
+the second one maximal.  The first works in more places than the second.
+.PP
+The \f(CW\*(C`use64bitint\*(C'\fR does only as much as is required to get 64\-bit
+integers into Perl (this may mean, for example, using "long longs")
+while your memory may still be limited to 2 gigabytes (because your
+pointers could still be 32\-bit).  Note that the name \f(CW\*(C`64bitint\*(C'\fR does
+not imply that your C compiler will be using 64\-bit \f(CW\*(C`int\*(C'\fRs (it might,
+but it doesn't have to): the \f(CW\*(C`use64bitint\*(C'\fR means that you will be
+able to have 64 bits wide scalar values.
+.PP
+The \f(CW\*(C`use64bitall\*(C'\fR goes all the way by attempting to switch also
+integers (if it can), longs (and pointers) to being 64\-bit.  This may
+create an even more binary incompatible Perl than \-Duse64bitint: the
+resulting executable may not run at all in a 32\-bit box, or you may
+have to reboot/reconfigure/rebuild your operating system to be 64\-bit
+aware.
+.PP
+Natively 64\-bit systems like Alpha and Cray need neither \-Duse64bitint
+nor \-Duse64bitall.
+.PP
+Last but not least: note that due to Perl's habit of always using
+floating point numbers, the quads are still not true integers.
+When quads overflow their limits (0...18_446_744_073_709_551_615 unsigned,
+\&\-9_223_372_036_854_775_808...9_223_372_036_854_775_807 signed), they
+are silently promoted to floating point numbers, after which they will
+start losing precision (in their lower digits).
+.PP
+.Vb 4
+\&    NOTE: 64\-bit support is still experimental on most platforms.
+\&    Existing support only covers the LP64 data model.  In particular, the
+\&    LLP64 data model is not yet supported.  64\-bit libraries and system
+\&    APIs on many platforms have not stabilized\-\-your mileage may vary.
+.Ve
+.SS "Large file support"
+.IX Subsection "Large file support"
+If you have filesystems that support "large files" (files larger than
+2 gigabytes), you may now also be able to create and access them from
+Perl.
+.PP
+.Vb 2
+\&    NOTE: The default action is to enable large file support, if
+\&    available on the platform.
+.Ve
+.PP
+If the large file support is on, and you have a Fcntl constant
+O_LARGEFILE, the O_LARGEFILE is automatically added to the flags
+of \fBsysopen()\fR.
+.PP
+Beware that unless your filesystem also supports "sparse files" seeking
+to umpteen petabytes may be inadvisable.
+.PP
+Note that in addition to requiring a proper file system to do large
+files you may also need to adjust your per-process (or your
+per-system, or per-process-group, or per-user-group) maximum filesize
+limits before running Perl scripts that try to handle large files,
+especially if you intend to write such files.
+.PP
+Finally, in addition to your process/process group maximum filesize
+limits, you may have quota limits on your filesystems that stop you
+(your user id or your user group id) from using large files.
+.PP
+Adjusting your process/user/group/file system/operating system limits
+is outside the scope of Perl core language.  For process limits, you
+may try increasing the limits using your shell's limits/limit/ulimit
+command before running Perl.  The BSD::Resource extension (not
+included with the standard Perl distribution) may also be of use, it
+offers the getrlimit/setrlimit interface that can be used to adjust
+process resource usage limits, including the maximum filesize limit.
+.SS "Long doubles"
+.IX Subsection "Long doubles"
+In some systems you may be able to use long doubles to enhance the
+range and precision of your double precision floating point numbers
+(that is, Perl's numbers).  Use Configure \-Duselongdouble to enable
+this support (if it is available).
+.SS """more bits"""
+.IX Subsection """more bits"""
+You can "Configure \-Dusemorebits" to turn on both the 64\-bit support
+and the long double support.
+.SS "Enhanced support for \fBsort()\fP subroutines"
+.IX Subsection "Enhanced support for sort() subroutines"
+Perl subroutines with a prototype of \f(CW\*(C`($$)\*(C'\fR, and XSUBs in general, can
+now be used as sort subroutines.  In either case, the two elements to
+be compared are passed as normal parameters in \f(CW@_\fR.  See "sort" in perlfunc.
+.PP
+For unprototyped sort subroutines, the historical behavior of passing 
+the elements to be compared as the global variables \f(CW$a\fR and \f(CW$b\fR remains
+unchanged.
+.ie n .SS """sort $coderef @foo"" allowed"
+.el .SS "\f(CWsort $coderef @foo\fP allowed"
+.IX Subsection "sort $coderef @foo allowed"
+\&\fBsort()\fR did not accept a subroutine reference as the comparison
+function in earlier versions.  This is now permitted.
+.SS "File globbing implemented internally"
+.IX Subsection "File globbing implemented internally"
+Perl now uses the File::Glob implementation of the \fBglob()\fR operator
+automatically.  This avoids using an external csh process and the
+problems associated with it.
+.PP
+.Vb 2
+\&    NOTE: This is currently an experimental feature.  Interfaces and
+\&    implementation are subject to change.
+.Ve
+.SS "Support for CHECK blocks"
+.IX Subsection "Support for CHECK blocks"
+In addition to \f(CW\*(C`BEGIN\*(C'\fR, \f(CW\*(C`INIT\*(C'\fR, \f(CW\*(C`END\*(C'\fR, \f(CW\*(C`DESTROY\*(C'\fR and \f(CW\*(C`AUTOLOAD\*(C'\fR,
+subroutines named \f(CW\*(C`CHECK\*(C'\fR are now special.  These are queued up during
+compilation and behave similar to END blocks, except they are called at
+the end of compilation rather than at the end of execution.  They cannot
+be called directly.
+.SS "POSIX character class syntax [: :] supported"
+.IX Subsection "POSIX character class syntax [: :] supported"
+For example to match alphabetic characters use /[[:alpha:]]/.
+See perlre for details.
+.SS "Better pseudo-random number generator"
+.IX Subsection "Better pseudo-random number generator"
+In 5.005_0x and earlier, perl's \fBrand()\fR function used the C library
+\&\fBrand\fR\|(3) function.  As of 5.005_52, Configure tests for \fBdrand48()\fR,
+\&\fBrandom()\fR, and \fBrand()\fR (in that order) and picks the first one it finds.
+.PP
+These changes should result in better random numbers from \fBrand()\fR.
+.ie n .SS "Improved ""qw//"" operator"
+.el .SS "Improved \f(CWqw//\fP operator"
+.IX Subsection "Improved qw// operator"
+The \f(CW\*(C`qw//\*(C'\fR operator is now evaluated at compile time into a true list
+instead of being replaced with a run time call to \f(CWsplit()\fR.  This
+removes the confusing misbehaviour of \f(CW\*(C`qw//\*(C'\fR in scalar context, which
+had inherited that behaviour from \fBsplit()\fR.
+.PP
+Thus:
+.PP
+.Vb 1
+\&    $foo = ($bar) = qw(a b c); print "$foo|$bar\en";
+.Ve
+.PP
+now correctly prints "3|a", instead of "2|a".
+.SS "Better worst-case behavior of hashes"
+.IX Subsection "Better worst-case behavior of hashes"
+Small changes in the hashing algorithm have been implemented in
+order to improve the distribution of lower order bits in the
+hashed value.  This is expected to yield better performance on
+keys that are repeated sequences.
+.SS "\fBpack()\fP format 'Z' supported"
+.IX Subsection "pack() format 'Z' supported"
+The new format type 'Z' is useful for packing and unpacking null-terminated
+strings.  See "pack" in perlfunc.
+.SS "\fBpack()\fP format modifier '!' supported"
+.IX Subsection "pack() format modifier '!' supported"
+The new format type modifier '!' is useful for packing and unpacking
+native shorts, ints, and longs.  See "pack" in perlfunc.
+.SS "\fBpack()\fP and \fBunpack()\fP support counted strings"
+.IX Subsection "pack() and unpack() support counted strings"
+The template character '/' can be used to specify a counted string
+type to be packed or unpacked.  See "pack" in perlfunc.
+.SS "Comments in \fBpack()\fP templates"
+.IX Subsection "Comments in pack() templates"
+The '#' character in a template introduces a comment up to
+end of the line.  This facilitates documentation of \fBpack()\fR
+templates.
+.SS "Weak references"
+.IX Subsection "Weak references"
+In previous versions of Perl, you couldn't cache objects so as
+to allow them to be deleted if the last reference from outside 
+the cache is deleted.  The reference in the cache would hold a
+reference count on the object and the objects would never be
+destroyed.
+.PP
+Another familiar problem is with circular references.  When an
+object references itself, its reference count would never go
+down to zero, and it would not get destroyed until the program
+is about to exit.
+.PP
+Weak references solve this by allowing you to "weaken" any
+reference, that is, make it not count towards the reference count.
+When the last non-weak reference to an object is deleted, the object
+is destroyed and all the weak references to the object are
+automatically undef-ed.
+.PP
+To use this feature, you need the Devel::WeakRef package from CPAN, which
+contains additional documentation.
+.PP
+.Vb 1
+\&    NOTE: This is an experimental feature.  Details are subject to change.
+.Ve
+.SS "Binary numbers supported"
+.IX Subsection "Binary numbers supported"
+Binary numbers are now supported as literals, in s?printf formats, and
+\&\f(CWoct()\fR:
+.PP
+.Vb 2
+\&    $answer = 0b101010;
+\&    printf "The answer is: %b\en", oct("0b101010");
+.Ve
+.SS "Lvalue subroutines"
+.IX Subsection "Lvalue subroutines"
+Subroutines can now return modifiable lvalues.
+See "Lvalue subroutines" in perlsub.
+.PP
+.Vb 1
+\&    NOTE: This is an experimental feature.  Details are subject to change.
+.Ve
+.SS "Some arrows may be omitted in calls through references"
+.IX Subsection "Some arrows may be omitted in calls through references"
+Perl now allows the arrow to be omitted in many constructs
+involving subroutine calls through references.  For example,
+\&\f(CW\*(C`$foo[10]\->(\*(Aqfoo\*(Aq)\*(C'\fR may now be written \f(CW\*(C`$foo[10](\*(Aqfoo\*(Aq)\*(C'\fR.
+This is rather similar to how the arrow may be omitted from
+\&\f(CW\*(C`$foo[10]\->{\*(Aqfoo\*(Aq}\*(C'\fR.  Note however, that the arrow is still
+required for \f(CW\*(C`foo(10)\->(\*(Aqbar\*(Aq)\*(C'\fR.
+.SS "Boolean assignment operators are legal lvalues"
+.IX Subsection "Boolean assignment operators are legal lvalues"
+Constructs such as \f(CW\*(C`($a ||= 2) += 1\*(C'\fR are now allowed.
+.SS "\fBexists()\fP is supported on subroutine names"
+.IX Subsection "exists() is supported on subroutine names"
+The \fBexists()\fR builtin now works on subroutine names.  A subroutine
+is considered to exist if it has been declared (even if implicitly).
+See "exists" in perlfunc for examples.
+.SS "\fBexists()\fP and \fBdelete()\fP are supported on array elements"
+.IX Subsection "exists() and delete() are supported on array elements"
+The \fBexists()\fR and \fBdelete()\fR builtins now work on simple arrays as well.
+The behavior is similar to that on hash elements.
+.PP
+\&\fBexists()\fR can be used to check whether an array element has been
+initialized.  This avoids autovivifying array elements that don't exist.
+If the array is tied, the \fBEXISTS()\fR method in the corresponding tied
+package will be invoked.
+.PP
+\&\fBdelete()\fR may be used to remove an element from the array and return
+it.  The array element at that position returns to its uninitialized
+state, so that testing for the same element with \fBexists()\fR will return
+false.  If the element happens to be the one at the end, the size of
+the array also shrinks up to the highest element that tests true for
+\&\fBexists()\fR, or 0 if none such is found.  If the array is tied, the \fBDELETE()\fR 
+method in the corresponding tied package will be invoked.
+.PP
+See "exists" in perlfunc and "delete" in perlfunc for examples.
+.SS "Pseudo-hashes work better"
+.IX Subsection "Pseudo-hashes work better"
+Dereferencing some types of reference values in a pseudo-hash,
+such as \f(CW\*(C`$ph\->{foo}[1]\*(C'\fR, was accidentally disallowed.  This has
+been corrected.
+.PP
+When applied to a pseudo-hash element, \fBexists()\fR now reports whether
+the specified value exists, not merely if the key is valid.
+.PP
+\&\fBdelete()\fR now works on pseudo-hashes.  When given a pseudo-hash element
+or slice it deletes the values corresponding to the keys (but not the keys
+themselves).  See "Pseudo-hashes: Using an array as a hash" in perlref.
+.PP
+Pseudo-hash slices with constant keys are now optimized to array lookups
+at compile-time.
+.PP
+List assignments to pseudo-hash slices are now supported.
+.PP
+The \f(CW\*(C`fields\*(C'\fR pragma now provides ways to create pseudo-hashes, via
+\&\fBfields::new()\fR and \fBfields::phash()\fR.  See fields.
+.PP
+.Vb 3
+\&    NOTE: The pseudo\-hash data type continues to be experimental.
+\&    Limiting oneself to the interface elements provided by the
+\&    fields pragma will provide protection from any future changes.
+.Ve
+.SS "Automatic flushing of output buffers"
+.IX Subsection "Automatic flushing of output buffers"
+\&\fBfork()\fR, \fBexec()\fR, \fBsystem()\fR, qx//, and pipe \fBopen()\fRs now flush buffers
+of all files opened for output when the operation was attempted.  This
+mostly eliminates confusing buffering mishaps suffered by users unaware
+of how Perl internally handles I/O.
+.PP
+This is not supported on some platforms like Solaris where a suitably
+correct implementation of fflush(NULL) isn't available.
+.SS "Better diagnostics on meaningless filehandle operations"
+.IX Subsection "Better diagnostics on meaningless filehandle operations"
+Constructs such as \f(CWopen(<FH>)\fR and \f(CWclose(<FH>)\fR
+are compile time errors.  Attempting to read from filehandles that
+were opened only for writing will now produce warnings (just as
+writing to read-only filehandles does).
+.SS "Where possible, buffered data discarded from duped input filehandle"
+.IX Subsection "Where possible, buffered data discarded from duped input filehandle"
+\&\f(CW\*(C`open(NEW, "<&OLD")\*(C'\fR now attempts to discard any data that
+was previously read and buffered in \f(CW\*(C`OLD\*(C'\fR before duping the handle.
+On platforms where doing this is allowed, the next read operation
+on \f(CW\*(C`NEW\*(C'\fR will return the same data as the corresponding operation
+on \f(CW\*(C`OLD\*(C'\fR.  Formerly, it would have returned the data from the start
+of the following disk block instead.
+.SS "\fBeof()\fP has the same old magic as <>"
+.IX Subsection "eof() has the same old magic as <>"
+\&\f(CWeof()\fR would return true if no attempt to read from \f(CW\*(C`<>\*(C'\fR had
+yet been made.  \f(CWeof()\fR has been changed to have a little magic of its
+own, it now opens the \f(CW\*(C`<>\*(C'\fR files.
+.SS "\fBbinmode()\fP can be used to set :crlf and :raw modes"
+.IX Subsection "binmode() can be used to set :crlf and :raw modes"
+\&\fBbinmode()\fR now accepts a second argument that specifies a discipline
+for the handle in question.  The two pseudo-disciplines ":raw" and
+":crlf" are currently supported on DOS-derivative platforms.
+See "binmode" in perlfunc and open.
+.ie n .SS """\-T"" filetest recognizes UTF\-8 encoded files as ""text"""
+.el .SS "\f(CW\-T\fP filetest recognizes UTF\-8 encoded files as ""text"""
+.IX Subsection "-T filetest recognizes UTF-8 encoded files as ""text"""
+The algorithm used for the \f(CW\*(C`\-T\*(C'\fR filetest has been enhanced to
+correctly identify UTF\-8 content as "text".
+.SS "\fBsystem()\fP, backticks and pipe open now reflect \fBexec()\fP failure"
+.IX Subsection "system(), backticks and pipe open now reflect exec() failure"
+On Unix and similar platforms, \fBsystem()\fR, \fBqx()\fR and open(FOO, "cmd |")
+etc., are implemented via \fBfork()\fR and \fBexec()\fR.  When the underlying
+\&\fBexec()\fR fails, earlier versions did not report the error properly,
+since the \fBexec()\fR happened to be in a different process.
+.PP
+The child process now communicates with the parent about the
+error in launching the external command, which allows these
+constructs to return with their usual error value and set $!.
+.SS "Improved diagnostics"
+.IX Subsection "Improved diagnostics"
+Line numbers are no longer suppressed (under most likely circumstances)
+during the global destruction phase.
+.PP
+Diagnostics emitted from code running in threads other than the main
+thread are now accompanied by the thread ID.
+.PP
+Embedded null characters in diagnostics now actually show up.  They
+used to truncate the message in prior versions.
+.PP
+\&\f(CW$foo::a\fR and \f(CW$foo::b\fR are now exempt from "possible typo" warnings only
+if \fBsort()\fR is encountered in package \f(CW\*(C`foo\*(C'\fR.
+.PP
+Unrecognized alphabetic escapes encountered when parsing quote
+constructs now generate a warning, since they may take on new
+semantics in later versions of Perl.
+.PP
+Many diagnostics now report the internal operation in which the warning
+was provoked, like so:
+.PP
+.Vb 2
+\&    Use of uninitialized value in concatenation (.) at (eval 1) line 1.
+\&    Use of uninitialized value in print at (eval 1) line 1.
+.Ve
+.PP
+Diagnostics  that occur within eval may also report the file and line
+number where the eval is located, in addition to the eval sequence
+number and the line number within the evaluated text itself.  For
+example:
+.PP
+.Vb 1
+\&    Not enough arguments for scalar at (eval 4)[newlib/perl5db.pl:1411] line 2, at EOF
+.Ve
+.SS "Diagnostics follow STDERR"
+.IX Subsection "Diagnostics follow STDERR"
+Diagnostic output now goes to whichever file the \f(CW\*(C`STDERR\*(C'\fR handle
+is pointing at, instead of always going to the underlying C runtime
+library's \f(CW\*(C`stderr\*(C'\fR.
+.SS "More consistent close-on-exec behavior"
+.IX Subsection "More consistent close-on-exec behavior"
+On systems that support a close-on-exec flag on filehandles, the
+flag is now set for any handles created by \fBpipe()\fR, \fBsocketpair()\fR,
+\&\fBsocket()\fR, and \fBaccept()\fR, if that is warranted by the value of $^F
+that may be in effect.  Earlier versions neglected to set the flag
+for handles created with these operators.  See "pipe" in perlfunc,
+"socketpair" in perlfunc, "socket" in perlfunc, "accept" in perlfunc,
+and "$^F" in perlvar.
+.SS "\fBsyswrite()\fP ease-of-use"
+.IX Subsection "syswrite() ease-of-use"
+The length argument of \f(CWsyswrite()\fR has become optional.
+.SS "Better syntax checks on parenthesized unary operators"
+.IX Subsection "Better syntax checks on parenthesized unary operators"
+Expressions such as:
+.PP
+.Vb 3
+\&    print defined(&foo,&bar,&baz);
+\&    print uc("foo","bar","baz");
+\&    undef($foo,&bar);
+.Ve
+.PP
+used to be accidentally allowed in earlier versions, and produced
+unpredictable behaviour.  Some produced ancillary warnings
+when used in this way; others silently did the wrong thing.
+.PP
+The parenthesized forms of most unary operators that expect a single
+argument now ensure that they are not called with more than one
+argument, making the cases shown above syntax errors.  The usual
+behaviour of:
+.PP
+.Vb 3
+\&    print defined &foo, &bar, &baz;
+\&    print uc "foo", "bar", "baz";
+\&    undef $foo, &bar;
+.Ve
+.PP
+remains unchanged.  See perlop.
+.SS "Bit operators support full native integer width"
+.IX Subsection "Bit operators support full native integer width"
+The bit operators (& | ^ ~ << >>) now operate on the full native
+integral width (the exact size of which is available in \f(CW$Config\fR{ivsize}).
+For example, if your platform is either natively 64\-bit or if Perl
+has been configured to use 64\-bit integers, these operations apply
+to 8 bytes (as opposed to 4 bytes on 32\-bit platforms).
+For portability, be sure to mask off the excess bits in the result of
+unary \f(CW\*(C`~\*(C'\fR, e.g., \f(CW\*(C`~$x & 0xffffffff\*(C'\fR.
+.SS "Improved security features"
+.IX Subsection "Improved security features"
+More potentially unsafe operations taint their results for improved
+security.
+.PP
+The \f(CW\*(C`passwd\*(C'\fR and \f(CW\*(C`shell\*(C'\fR fields returned by the \fBgetpwent()\fR, \fBgetpwnam()\fR,
+and \fBgetpwuid()\fR are now tainted, because the user can affect their own
+encrypted password and login shell.
+.PP
+The variable modified by \fBshmread()\fR, and messages returned by \fBmsgrcv()\fR
+(and its object-oriented interface IPC::SysV::Msg::rcv) are also tainted,
+because other untrusted processes can modify messages and shared memory
+segments for their own nefarious purposes.
+.SS "More functional bareword prototype (*)"
+.IX Subsection "More functional bareword prototype (*)"
+Bareword prototypes have been rationalized to enable them to be used
+to override builtins that accept barewords and interpret them in
+a special way, such as \f(CW\*(C`require\*(C'\fR or \f(CW\*(C`do\*(C'\fR.
+.PP
+Arguments prototyped as \f(CW\*(C`*\*(C'\fR will now be visible within the subroutine
+as either a simple scalar or as a reference to a typeglob.
+See "Prototypes" in perlsub.
+.ie n .SS """require"" and ""do"" may be overridden"
+.el .SS "\f(CWrequire\fP and \f(CWdo\fP may be overridden"
+.IX Subsection "require and do may be overridden"
+\&\f(CW\*(C`require\*(C'\fR and \f(CW\*(C`do \*(Aqfile\*(Aq\*(C'\fR operations may be overridden locally
+by importing subroutines of the same name into the current package 
+(or globally by importing them into the CORE::GLOBAL:: namespace).
+Overriding \f(CW\*(C`require\*(C'\fR will also affect \f(CW\*(C`use\*(C'\fR, provided the override
+is visible at compile-time.
+See "Overriding Built-in Functions" in perlsub.
+.SS "$^X variables may now have names longer than one character"
+.IX Subsection "$^X variables may now have names longer than one character"
+Formerly, $^X was synonymous with ${"\ecX"}, but $^XY was a syntax
+error.  Now variable names that begin with a control character may be
+arbitrarily long.  However, for compatibility reasons, these variables
+\&\fImust\fR be written with explicit braces, as \f(CW\*(C`${^XY}\*(C'\fR for example.
+\&\f(CW\*(C`${^XYZ}\*(C'\fR is synonymous with ${"\ecXYZ"}.  Variable names with more
+than one control character, such as \f(CW\*(C`${^XY^Z}\*(C'\fR, are illegal.
+.PP
+The old syntax has not changed.  As before, `^X' may be either a
+literal control-X character or the two-character sequence `caret' plus
+`X'.  When braces are omitted, the variable name stops after the
+control character.  Thus \f(CW"$^XYZ"\fR continues to be synonymous with
+\&\f(CW\*(C`$^X . "YZ"\*(C'\fR as before.
+.PP
+As before, lexical variables may not have names beginning with control
+characters.  As before, variables whose names begin with a control
+character are always forced to be in package `main'.  All such variables
+are reserved for future extensions, except those that begin with
+\&\f(CW\*(C`^_\*(C'\fR, which may be used by user programs and are guaranteed not to
+acquire special meaning in any future version of Perl.
+.ie n .SS "New variable $^C reflects ""\-c"" switch"
+.el .SS "New variable $^C reflects \f(CW\-c\fP switch"
+.IX Subsection "New variable $^C reflects -c switch"
+\&\f(CW$^C\fR has a boolean value that reflects whether perl is being run
+in compile-only mode (i.e. via the \f(CW\*(C`\-c\*(C'\fR switch).  Since
+BEGIN blocks are executed under such conditions, this variable
+enables perl code to determine whether actions that make sense
+only during normal running are warranted.  See perlvar.
+.SS "New variable $^V contains Perl version as a string"
+.IX Subsection "New variable $^V contains Perl version as a string"
+\&\f(CW$^V\fR contains the Perl version number as a string composed of
+characters whose ordinals match the version numbers, i.e. v5.6.0.
+This may be used in string comparisons.
+.PP
+See \f(CW\*(C`Support for strings represented as a vector of ordinals\*(C'\fR for an
+example.
+.SS "Optional Y2K warnings"
+.IX Subsection "Optional Y2K warnings"
+If Perl is built with the cpp macro \f(CW\*(C`PERL_Y2KWARN\*(C'\fR defined,
+it emits optional warnings when concatenating the number 19
+with another number.
+.PP
+This behavior must be specifically enabled when running Configure.
+See \fIINSTALL\fR and \fIREADME.Y2K\fR.
+.SS "Arrays now always interpolate into double-quoted strings"
+.IX Subsection "Arrays now always interpolate into double-quoted strings"
+In double-quoted strings, arrays now interpolate, no matter what.  The
+behavior in earlier versions of perl 5 was that arrays would interpolate
+into strings if the array had been mentioned before the string was
+compiled, and otherwise Perl would raise a fatal compile-time error.
+In versions 5.000 through 5.003, the error was
+.PP
+.Vb 1
+\&        Literal @example now requires backslash
+.Ve
+.PP
+In versions 5.004_01 through 5.6.0, the error was
+.PP
+.Vb 1
+\&        In string, @example now must be written as \e@example
+.Ve
+.PP
+The idea here was to get people into the habit of writing
+\&\f(CW"fred\e@example.com"\fR when they wanted a literal \f(CW\*(C`@\*(C'\fR sign, just as
+they have always written \f(CW"Give me back my \e$5"\fR when they wanted a
+literal \f(CW\*(C`$\*(C'\fR sign.
+.PP
+Starting with 5.6.1, when Perl now sees an \f(CW\*(C`@\*(C'\fR sign in a
+double-quoted string, it \fIalways\fR attempts to interpolate an array,
+regardless of whether or not the array has been used or declared
+already.  The fatal error has been downgraded to an optional warning:
+.PP
+.Vb 1
+\&        Possible unintended interpolation of @example in string
+.Ve
+.PP
+This warns you that \f(CW"fred@example.com"\fR is going to turn into
+\&\f(CW\*(C`fred.com\*(C'\fR if you don't backslash the \f(CW\*(C`@\*(C'\fR.
+See http://perl.plover.com/at\-error.html for more details
+about the history here.
+.SS "@\- and @+ provide starting/ending offsets of regex matches"
+.IX Subsection "@- and @+ provide starting/ending offsets of regex matches"
+The new magic variables @\- and @+ provide the starting and ending
+offsets, respectively, of $&, \f(CW$1\fR, \f(CW$2\fR, etc.  See perlvar for
+details.
+.SH "Modules and Pragmata"
+.IX Header "Modules and Pragmata"
+.SS Modules
+.IX Subsection "Modules"
+.IP attributes 4
+.IX Item "attributes"
+While used internally by Perl as a pragma, this module also
+provides a way to fetch subroutine and variable attributes.
+See attributes.
+.IP B 4
+.IX Item "B"
+The Perl Compiler suite has been extensively reworked for this
+release.  More of the standard Perl test suite passes when run
+under the Compiler, but there is still a significant way to
+go to achieve production quality compiled executables.
+.Sp
+.Vb 3
+\&    NOTE: The Compiler suite remains highly experimental.  The
+\&    generated code may not be correct, even when it manages to execute
+\&    without errors.
+.Ve
+.IP Benchmark 4
+.IX Item "Benchmark"
+Overall, Benchmark results exhibit lower average error and better timing
+accuracy.
+.Sp
+You can now run tests for \fIn\fR seconds instead of guessing the right
+number of tests to run: e.g., timethese(\-5, ...) will run each 
+code for at least 5 CPU seconds.  Zero as the "number of repetitions"
+means "for at least 3 CPU seconds".  The output format has also
+changed.  For example:
+.Sp
+.Vb 1
+\&   use Benchmark;$x=3;timethese(\-5,{a=>sub{$x*$x},b=>sub{$x**2}})
+.Ve
+.Sp
+will now output something like this:
+.Sp
+.Vb 3
+\&   Benchmark: running a, b, each for at least 5 CPU seconds...
+\&            a:  5 wallclock secs ( 5.77 usr +  0.00 sys =  5.77 CPU) @ 200551.91/s (n=1156516)
+\&            b:  4 wallclock secs ( 5.00 usr +  0.02 sys =  5.02 CPU) @ 159605.18/s (n=800686)
+.Ve
+.Sp
+New features: "each for at least N CPU seconds...", "wallclock secs",
+and the "@ operations/CPU second (n=operations)".
+.Sp
+\&\fBtimethese()\fR now returns a reference to a hash of Benchmark objects containing
+the test results, keyed on the names of the tests.
+.Sp
+\&\fBtimethis()\fR now returns the iterations field in the Benchmark result object
+instead of 0.
+.Sp
+\&\fBtimethese()\fR, \fBtimethis()\fR, and the new \fBcmpthese()\fR (see below) can also take
+a format specifier of 'none' to suppress output.
+.Sp
+A new function \fBcountit()\fR is just like \fBtimeit()\fR except that it takes a
+TIME instead of a COUNT.
+.Sp
+A new function \fBcmpthese()\fR prints a chart comparing the results of each test
+returned from a \fBtimethese()\fR call.  For each possible pair of tests, the
+percentage speed difference (iters/sec or seconds/iter) is shown.
+.Sp
+For other details, see Benchmark.
+.IP ByteLoader 4
+.IX Item "ByteLoader"
+The ByteLoader is a dedicated extension to generate and run
+Perl bytecode.  See ByteLoader.
+.IP constant 4
+.IX Item "constant"
+References can now be used.
+.Sp
+The new version also allows a leading underscore in constant names, but
+disallows a double leading underscore (as in "_\|_LINE_\|_").  Some other names
+are disallowed or warned against, including BEGIN, END, etc.  Some names
+which were forced into main:: used to fail silently in some cases; now they're
+fatal (outside of main::) and an optional warning (inside of main::).
+The ability to detect whether a constant had been set with a given name has
+been added.
+.Sp
+See constant.
+.IP charnames 4
+.IX Item "charnames"
+This pragma implements the \f(CW\*(C`\eN\*(C'\fR string escape.  See charnames.
+.IP Data::Dumper 4
+.IX Item "Data::Dumper"
+A \f(CW\*(C`Maxdepth\*(C'\fR setting can be specified to avoid venturing
+too deeply into deep data structures.  See Data::Dumper.
+.Sp
+The XSUB implementation of \fBDump()\fR is now automatically called if the
+\&\f(CW\*(C`Useqq\*(C'\fR setting is not in use.
+.Sp
+Dumping \f(CW\*(C`qr//\*(C'\fR objects works correctly.
+.IP DB 4
+.IX Item "DB"
+\&\f(CW\*(C`DB\*(C'\fR is an experimental module that exposes a clean abstraction
+to Perl's debugging API.
+.IP DB_File 4
+.IX Item "DB_File"
+DB_File can now be built with Berkeley DB versions 1, 2 or 3.
+See \f(CW\*(C`ext/DB_File/Changes\*(C'\fR.
+.IP Devel::DProf 4
+.IX Item "Devel::DProf"
+Devel::DProf, a Perl source code profiler has been added.  See
+Devel::DProf and dprofpp.
+.IP Devel::Peek 4
+.IX Item "Devel::Peek"
+The Devel::Peek module provides access to the internal representation
+of Perl variables and data.  It is a data debugging tool for the XS programmer.
+.IP Dumpvalue 4
+.IX Item "Dumpvalue"
+The Dumpvalue module provides screen dumps of Perl data.
+.IP DynaLoader 4
+.IX Item "DynaLoader"
+DynaLoader now supports a \fBdl_unload_file()\fR function on platforms that
+support unloading shared objects using \fBdlclose()\fR.
+.Sp
+Perl can also optionally arrange to unload all extension shared objects
+loaded by Perl.  To enable this, build Perl with the Configure option
+\&\f(CW\*(C`\-Accflags=\-DDL_UNLOAD_ALL_AT_EXIT\*(C'\fR.  (This maybe useful if you are
+using Apache with mod_perl.)
+.IP English 4
+.IX Item "English"
+\&\f(CW$PERL_VERSION\fR now stands for \f(CW$^V\fR (a string value) rather than for \f(CW$]\fR
+(a numeric value).
+.IP Env 4
+.IX Item "Env"
+Env now supports accessing environment variables like PATH as array
+variables.
+.IP Fcntl 4
+.IX Item "Fcntl"
+More Fcntl constants added: F_SETLK64, F_SETLKW64, O_LARGEFILE for
+large file (more than 4GB) access (NOTE: the O_LARGEFILE is
+automatically added to \fBsysopen()\fR flags if large file support has been
+configured, as is the default), Free/Net/OpenBSD locking behaviour
+flags F_FLOCK, F_POSIX, Linux F_SHLCK, and O_ACCMODE: the combined
+mask of O_RDONLY, O_WRONLY, and O_RDWR.  The \fBseek()\fR/\fBsysseek()\fR
+constants SEEK_SET, SEEK_CUR, and SEEK_END are available via the
+\&\f(CW\*(C`:seek\*(C'\fR tag.  The \fBchmod()\fR/\fBstat()\fR S_IF* constants and S_IS* functions
+are available via the \f(CW\*(C`:mode\*(C'\fR tag.
+.IP File::Compare 4
+.IX Item "File::Compare"
+A \fBcompare_text()\fR function has been added, which allows custom
+comparison functions.  See File::Compare.
+.IP File::Find 4
+.IX Item "File::Find"
+File::Find now works correctly when the \fBwanted()\fR function is either
+autoloaded or is a symbolic reference.
+.Sp
+A bug that caused File::Find to lose track of the working directory
+when pruning top-level directories has been fixed.
+.Sp
+File::Find now also supports several other options to control its
+behavior.  It can follow symbolic links if the \f(CW\*(C`follow\*(C'\fR option is
+specified.  Enabling the \f(CW\*(C`no_chdir\*(C'\fR option will make File::Find skip
+changing the current directory when walking directories.  The \f(CW\*(C`untaint\*(C'\fR
+flag can be useful when running with taint checks enabled.
+.Sp
+See File::Find.
+.IP File::Glob 4
+.IX Item "File::Glob"
+This extension implements BSD-style file globbing.  By default,
+it will also be used for the internal implementation of the \fBglob()\fR
+operator.  See File::Glob.
+.IP File::Spec 4
+.IX Item "File::Spec"
+New methods have been added to the File::Spec module: \fBdevnull()\fR returns
+the name of the null device (/dev/null on Unix) and \fBtmpdir()\fR the name of
+the temp directory (normally /tmp on Unix).  There are now also methods
+to convert between absolute and relative filenames: \fBabs2rel()\fR and
+\&\fBrel2abs()\fR.  For compatibility with operating systems that specify volume
+names in file paths, the \fBsplitpath()\fR, \fBsplitdir()\fR, and \fBcatdir()\fR methods
+have been added.
+.IP File::Spec::Functions 4
+.IX Item "File::Spec::Functions"
+The new File::Spec::Functions modules provides a function interface
+to the File::Spec module.  Allows shorthand
+.Sp
+.Vb 1
+\&    $fullname = catfile($dir1, $dir2, $file);
+.Ve
+.Sp
+instead of
+.Sp
+.Vb 1
+\&    $fullname = File::Spec\->catfile($dir1, $dir2, $file);
+.Ve
+.IP Getopt::Long 4
+.IX Item "Getopt::Long"
+Getopt::Long licensing has changed to allow the Perl Artistic License
+as well as the GPL. It used to be GPL only, which got in the way of
+non-GPL applications that wanted to use Getopt::Long.
+.Sp
+Getopt::Long encourages the use of Pod::Usage to produce help
+messages. For example:
+.Sp
+.Vb 7
+\&    use Getopt::Long;
+\&    use Pod::Usage;
+\&    my $man = 0;
+\&    my $help = 0;
+\&    GetOptions(\*(Aqhelp|?\*(Aq => \e$help, man => \e$man) or pod2usage(2);
+\&    pod2usage(1) if $help;
+\&    pod2usage(\-exitstatus => 0, \-verbose => 2) if $man;
+\&
+\&    _\|_END_\|_
+\&
+\&    =head1 NAME
+\&
+\&    sample \- Using Getopt::Long and Pod::Usage
+\&
+\&    =head1 SYNOPSIS
+\&
+\&    sample [options] [file ...]
+\&
+\&     Options:
+\&       \-help            brief help message
+\&       \-man             full documentation
+\&
+\&    =head1 OPTIONS
+\&
+\&    =over 8
+\&
+\&    =item B<\-help>
+\&
+\&    Print a brief help message and exits.
+\&
+\&    =item B<\-man>
+\&
+\&    Prints the manual page and exits.
+\&
+\&    =back
+\&
+\&    =head1 DESCRIPTION
+\&
+\&    B<This program> will read the given input file(s) and do something
+\&    useful with the contents thereof.
+\&
+\&    =cut
+.Ve
+.Sp
+See Pod::Usage for details.
+.Sp
+A bug that prevented the non-option call-back <> from being
+specified as the first argument has been fixed.
+.Sp
+To specify the characters < and > as option starters, use ><. Note,
+however, that changing option starters is strongly deprecated.
+.IP IO 4
+.IX Item "IO"
+\&\fBwrite()\fR and \fBsyswrite()\fR will now accept a single-argument
+form of the call, for consistency with Perl's \fBsyswrite()\fR.
+.Sp
+You can now create a TCP-based IO::Socket::INET without forcing
+a connect attempt.  This allows you to configure its options
+(like making it non-blocking) and then call \fBconnect()\fR manually.
+.Sp
+A bug that prevented the \fBIO::Socket::protocol()\fR accessor
+from ever returning the correct value has been corrected.
+.Sp
+IO::Socket::connect now uses non-blocking IO instead of \fBalarm()\fR
+to do connect timeouts.
+.Sp
+IO::Socket::accept now uses \fBselect()\fR instead of \fBalarm()\fR for doing
+timeouts.
+.Sp
+IO::Socket::INET\->new now sets $! correctly on failure. $@ is
+still set for backwards compatibility.
+.IP JPL 4
+.IX Item "JPL"
+Java Perl Lingo is now distributed with Perl.  See jpl/README
+for more information.
+.IP lib 4
+.IX Item "lib"
+\&\f(CW\*(C`use lib\*(C'\fR now weeds out any trailing duplicate entries.
+\&\f(CW\*(C`no lib\*(C'\fR removes all named entries.
+.IP Math::BigInt 4
+.IX Item "Math::BigInt"
+The bitwise operations \f(CW\*(C`<<\*(C'\fR, \f(CW\*(C`>>\*(C'\fR, \f(CW\*(C`&\*(C'\fR, \f(CW\*(C`|\*(C'\fR,
+and \f(CW\*(C`~\*(C'\fR are now supported on bigints.
+.IP Math::Complex 4
+.IX Item "Math::Complex"
+The accessor methods Re, Im, arg, abs, rho, and theta can now also
+act as mutators (accessor \f(CW$z\fR\->\fBRe()\fR, mutator \f(CW$z\fR\->\fBRe\fR\|(3)).
+.Sp
+The class method \f(CW\*(C`display_format\*(C'\fR and the corresponding object method
+\&\f(CW\*(C`display_format\*(C'\fR, in addition to accepting just one argument, now can
+also accept a parameter hash.  Recognized keys of a parameter hash are
+\&\f(CW"style"\fR, which corresponds to the old one parameter case, and two
+new parameters: \f(CW"format"\fR, which is a \fBprintf()\fR\-style format string
+(defaults usually to \f(CW"%.15g"\fR, you can revert to the default by
+setting the format string to \f(CW\*(C`undef\*(C'\fR) used for both parts of a
+complex number, and \f(CW"polar_pretty_print"\fR (defaults to true),
+which controls whether an attempt is made to try to recognize small
+multiples and rationals of pi (2pi, pi/2) at the argument (angle) of a
+polar complex number.
+.Sp
+The potentially disruptive change is that in list context both methods
+now \fIreturn the parameter hash\fR, instead of only the value of the
+\&\f(CW"style"\fR parameter.
+.IP Math::Trig 4
+.IX Item "Math::Trig"
+A little bit of radial trigonometry (cylindrical and spherical),
+radial coordinate conversions, and the great circle distance were added.
+.IP "Pod::Parser, Pod::InputObjects" 4
+.IX Item "Pod::Parser, Pod::InputObjects"
+Pod::Parser is a base class for parsing and selecting sections of
+pod documentation from an input stream.  This module takes care of
+identifying pod paragraphs and commands in the input and hands off the
+parsed paragraphs and commands to user-defined methods which are free
+to interpret or translate them as they see fit.
+.Sp
+Pod::InputObjects defines some input objects needed by Pod::Parser, and
+for advanced users of Pod::Parser that need more about a command besides
+its name and text.
+.Sp
+As of release 5.6.0 of Perl, Pod::Parser is now the officially sanctioned
+"base parser code" recommended for use by all pod2xxx translators.
+Pod::Text (pod2text) and Pod::Man (pod2man) have already been converted
+to use Pod::Parser and efforts to convert Pod::HTML (pod2html) are already
+underway.  For any questions or comments about pod parsing and translating
+issues and utilities, please use the pod\-people@perl.org mailing list.
+.Sp
+For further information, please see Pod::Parser and Pod::InputObjects.
+.IP "Pod::Checker, podchecker" 4
+.IX Item "Pod::Checker, podchecker"
+This utility checks pod files for correct syntax, according to
+perlpod.  Obvious errors are flagged as such, while warnings are
+printed for mistakes that can be handled gracefully.  The checklist is
+not complete yet.  See Pod::Checker.
+.IP "Pod::ParseUtils, Pod::Find" 4
+.IX Item "Pod::ParseUtils, Pod::Find"
+These modules provide a set of gizmos that are useful mainly for pod
+translators.  Pod::Find traverses directory structures and
+returns found pod files, along with their canonical names (like
+\&\f(CW\*(C`File::Spec::Unix\*(C'\fR).  Pod::ParseUtils contains
+\&\fBPod::List\fR (useful for storing pod list information), \fBPod::Hyperlink\fR
+(for parsing the contents of \f(CW\*(C`L<>\*(C'\fR sequences) and \fBPod::Cache\fR
+(for caching information about pod files, e.g., link nodes).
+.IP "Pod::Select, podselect" 4
+.IX Item "Pod::Select, podselect"
+Pod::Select is a subclass of Pod::Parser which provides a function
+named "\fBpodselect()\fR" to filter out user-specified sections of raw pod
+documentation from an input stream. podselect is a script that provides
+access to Pod::Select from other scripts to be used as a filter.
+See Pod::Select.
+.IP "Pod::Usage, pod2usage" 4
+.IX Item "Pod::Usage, pod2usage"
+Pod::Usage provides the function "\fBpod2usage()\fR" to print usage messages for
+a Perl script based on its embedded pod documentation.  The \fBpod2usage()\fR
+function is generally useful to all script authors since it lets them
+write and maintain a single source (the pods) for documentation, thus
+removing the need to create and maintain redundant usage message text
+consisting of information already in the pods.
+.Sp
+There is also a pod2usage script which can be used from other kinds of
+scripts to print usage messages from pods (even for non-Perl scripts
+with pods embedded in comments).
+.Sp
+For details and examples, please see Pod::Usage.
+.IP "Pod::Text and Pod::Man" 4
+.IX Item "Pod::Text and Pod::Man"
+Pod::Text has been rewritten to use Pod::Parser.  While \fBpod2text()\fR is
+still available for backwards compatibility, the module now has a new
+preferred interface.  See Pod::Text for the details.  The new Pod::Text
+module is easily subclassed for tweaks to the output, and two such
+subclasses (Pod::Text::Termcap for man-page-style bold and underlining
+using termcap information, and Pod::Text::Color for markup with ANSI color
+sequences) are now standard.
+.Sp
+pod2man has been turned into a module, Pod::Man, which also uses
+Pod::Parser.  In the process, several outstanding bugs related to quotes
+in section headers, quoting of code escapes, and nested lists have been
+fixed.  pod2man is now a wrapper script around this module.
+.IP SDBM_File 4
+.IX Item "SDBM_File"
+An EXISTS method has been added to this module (and \fBsdbm_exists()\fR has
+been added to the underlying sdbm library), so one can now call exists
+on an SDBM_File tied hash and get the correct result, rather than a
+runtime error.
+.Sp
+A bug that may have caused data loss when more than one disk block
+happens to be read from the database in a single \fBFETCH()\fR has been
+fixed.
+.IP Sys::Syslog 4
+.IX Item "Sys::Syslog"
+Sys::Syslog now uses XSUBs to access facilities from syslog.h so it
+no longer requires syslog.ph to exist.
+.IP Sys::Hostname 4
+.IX Item "Sys::Hostname"
+Sys::Hostname now uses XSUBs to call the C library's \fBgethostname()\fR or
+\&\fBuname()\fR if they exist.
+.IP Term::ANSIColor 4
+.IX Item "Term::ANSIColor"
+Term::ANSIColor is a very simple module to provide easy and readable
+access to the ANSI color and highlighting escape sequences, supported by
+most ANSI terminal emulators.  It is now included standard.
+.IP Time::Local 4
+.IX Item "Time::Local"
+The \fBtimelocal()\fR and \fBtimegm()\fR functions used to silently return bogus
+results when the date fell outside the machine's integer range.  They
+now consistently \fBcroak()\fR if the date falls in an unsupported range.
+.IP Win32 4
+.IX Item "Win32"
+The error return value in list context has been changed for all functions
+that return a list of values.  Previously these functions returned a list
+with a single element \f(CW\*(C`undef\*(C'\fR if an error occurred.  Now these functions
+return the empty list in these situations.  This applies to the following
+functions:
+.Sp
+.Vb 2
+\&    Win32::FsType
+\&    Win32::GetOSVersion
+.Ve
+.Sp
+The remaining functions are unchanged and continue to return \f(CW\*(C`undef\*(C'\fR on
+error even in list context.
+.Sp
+The Win32::SetLastError(ERROR) function has been added as a complement
+to the \fBWin32::GetLastError()\fR function.
+.Sp
+The new Win32::GetFullPathName(FILENAME) returns the full absolute
+pathname for FILENAME in scalar context.  In list context it returns
+a two-element list containing the fully qualified directory name and
+the filename.  See Win32.
+.IP XSLoader 4
+.IX Item "XSLoader"
+The XSLoader extension is a simpler alternative to DynaLoader.
+See XSLoader.
+.IP "DBM Filters" 4
+.IX Item "DBM Filters"
+A new feature called "DBM Filters" has been added to all the
+DBM modules\-\-DB_File, GDBM_File, NDBM_File, ODBM_File, and SDBM_File.
+DBM Filters add four new methods to each DBM module:
+.Sp
+.Vb 4
+\&    filter_store_key
+\&    filter_store_value
+\&    filter_fetch_key
+\&    filter_fetch_value
+.Ve
+.Sp
+These can be used to filter key-value pairs before the pairs are
+written to the database or just after they are read from the database.
+See perldbmfilter for further information.
+.SS Pragmata
+.IX Subsection "Pragmata"
+\&\f(CW\*(C`use attrs\*(C'\fR is now obsolete, and is only provided for
+backward-compatibility.  It's been replaced by the \f(CW\*(C`sub : attributes\*(C'\fR
+syntax.  See "Subroutine Attributes" in perlsub and attributes.
+.PP
+Lexical warnings pragma, \f(CW\*(C`use warnings;\*(C'\fR, to control optional warnings.
+See perllexwarn.
+.PP
+\&\f(CW\*(C`use filetest\*(C'\fR to control the behaviour of filetests (\f(CW\*(C`\-r\*(C'\fR \f(CW\*(C`\-w\*(C'\fR
+\&...).  Currently only one subpragma implemented, "use filetest
+\&'access';", that uses \fBaccess\fR\|(2) or equivalent to check permissions
+instead of using \fBstat\fR\|(2) as usual.  This matters in filesystems
+where there are ACLs (access control lists): the \fBstat\fR\|(2) might lie,
+but \fBaccess\fR\|(2) knows better.
+.PP
+The \f(CW\*(C`open\*(C'\fR pragma can be used to specify default disciplines for
+handle constructors (e.g. \fBopen()\fR) and for qx//.  The two
+pseudo-disciplines \f(CW\*(C`:raw\*(C'\fR and \f(CW\*(C`:crlf\*(C'\fR are currently supported on
+DOS-derivative platforms (i.e. where binmode is not a no-op).
+See also "\fBbinmode()\fR can be used to set :crlf and :raw modes".
+.SH "Utility Changes"
+.IX Header "Utility Changes"
+.SS dprofpp
+.IX Subsection "dprofpp"
+\&\f(CW\*(C`dprofpp\*(C'\fR is used to display profile data generated using \f(CW\*(C`Devel::DProf\*(C'\fR.
+See dprofpp.
+.SS find2perl
+.IX Subsection "find2perl"
+The \f(CW\*(C`find2perl\*(C'\fR utility now uses the enhanced features of the File::Find
+module.  The \-depth and \-follow options are supported.  Pod documentation
+is also included in the script.
+.SS h2xs
+.IX Subsection "h2xs"
+The \f(CW\*(C`h2xs\*(C'\fR tool can now work in conjunction with \f(CW\*(C`C::Scan\*(C'\fR (available
+from CPAN) to automatically parse real-life header files.  The \f(CW\*(C`\-M\*(C'\fR,
+\&\f(CW\*(C`\-a\*(C'\fR, \f(CW\*(C`\-k\*(C'\fR, and \f(CW\*(C`\-o\*(C'\fR options are new.
+.SS perlcc
+.IX Subsection "perlcc"
+\&\f(CW\*(C`perlcc\*(C'\fR now supports the C and Bytecode backends.  By default,
+it generates output from the simple C backend rather than the
+optimized C backend.
+.PP
+Support for non-Unix platforms has been improved.
+.SS perldoc
+.IX Subsection "perldoc"
+\&\f(CW\*(C`perldoc\*(C'\fR has been reworked to avoid possible security holes.
+It will not by default let itself be run as the superuser, but you
+may still use the \fB\-U\fR switch to try to make it drop privileges
+first.
+.SS "The Perl Debugger"
+.IX Subsection "The Perl Debugger"
+Many bug fixes and enhancements were added to \fIperl5db.pl\fR, the
+Perl debugger.  The help documentation was rearranged.  New commands
+include \f(CW\*(C`< ?\*(C'\fR, \f(CW\*(C`> ?\*(C'\fR, and \f(CW\*(C`{ ?\*(C'\fR to list out current
+actions, \f(CW\*(C`man \fR\f(CIdocpage\fR\f(CW\*(C'\fR to run your doc viewer on some perl
+docset, and support for quoted options.  The help information was
+rearranged, and should be viewable once again if you're using \fBless\fR
+as your pager.  A serious security hole was plugged\-\-you should
+immediately remove all older versions of the Perl debugger as
+installed in previous releases, all the way back to perl3, from
+your system to avoid being bitten by this.
+.SH "Improved Documentation"
+.IX Header "Improved Documentation"
+Many of the platform-specific README files are now part of the perl
+installation.  See perl for the complete list.
+.IP perlapi.pod 4
+.IX Item "perlapi.pod"
+The official list of public Perl API functions.
+.IP perlboot.pod 4
+.IX Item "perlboot.pod"
+A tutorial for beginners on object-oriented Perl.
+.IP perlcompile.pod 4
+.IX Item "perlcompile.pod"
+An introduction to using the Perl Compiler suite.
+.IP perldbmfilter.pod 4
+.IX Item "perldbmfilter.pod"
+A howto document on using the DBM filter facility.
+.IP perldebug.pod 4
+.IX Item "perldebug.pod"
+All material unrelated to running the Perl debugger, plus all
+low-level guts-like details that risked crushing the casual user
+of the debugger, have been relocated from the old manpage to the
+next entry below.
+.IP perldebguts.pod 4
+.IX Item "perldebguts.pod"
+This new manpage contains excessively low-level material not related
+to the Perl debugger, but slightly related to debugging Perl itself.
+It also contains some arcane internal details of how the debugging
+process works that may only be of interest to developers of Perl
+debuggers.
+.IP perlfork.pod 4
+.IX Item "perlfork.pod"
+Notes on the \fBfork()\fR emulation currently available for the Windows platform.
+.IP perlfilter.pod 4
+.IX Item "perlfilter.pod"
+An introduction to writing Perl source filters.
+.IP perlhack.pod 4
+.IX Item "perlhack.pod"
+Some guidelines for hacking the Perl source code.
+.IP perlintern.pod 4
+.IX Item "perlintern.pod"
+A list of internal functions in the Perl source code.
+(List is currently empty.)
+.IP perllexwarn.pod 4
+.IX Item "perllexwarn.pod"
+Introduction and reference information about lexically scoped
+warning categories.
+.IP perlnumber.pod 4
+.IX Item "perlnumber.pod"
+Detailed information about numbers as they are represented in Perl.
+.IP perlopentut.pod 4
+.IX Item "perlopentut.pod"
+A tutorial on using \fBopen()\fR effectively.
+.IP perlreftut.pod 4
+.IX Item "perlreftut.pod"
+A tutorial that introduces the essentials of references.
+.IP perltootc.pod 4
+.IX Item "perltootc.pod"
+A tutorial on managing class data for object modules.
+.IP perltodo.pod 4
+.IX Item "perltodo.pod"
+Discussion of the most often wanted features that may someday be
+supported in Perl.
+.IP perlunicode.pod 4
+.IX Item "perlunicode.pod"
+An introduction to Unicode support features in Perl.
+.SH "Performance enhancements"
+.IX Header "Performance enhancements"
+.ie n .SS "Simple \fBsort()\fP using { $a <=> $b } and the like are optimized"
+.el .SS "Simple \fBsort()\fP using { \f(CW$a\fP <=> \f(CW$b\fP } and the like are optimized"
+.IX Subsection "Simple sort() using { $a <=> $b } and the like are optimized"
+Many common \fBsort()\fR operations using a simple inlined block are now
+optimized for faster performance.
+.SS "Optimized assignments to lexical variables"
+.IX Subsection "Optimized assignments to lexical variables"
+Certain operations in the RHS of assignment statements have been
+optimized to directly set the lexical variable on the LHS,
+eliminating redundant copying overheads.
+.SS "Faster subroutine calls"
+.IX Subsection "Faster subroutine calls"
+Minor changes in how subroutine calls are handled internally
+provide marginal improvements in performance.
+.SS "\fBdelete()\fP, \fBeach()\fP, \fBvalues()\fP and hash iteration are faster"
+.IX Subsection "delete(), each(), values() and hash iteration are faster"
+The hash values returned by \fBdelete()\fR, \fBeach()\fR, \fBvalues()\fR and hashes in a
+list context are the actual values in the hash, instead of copies.
+This results in significantly better performance, because it eliminates
+needless copying in most situations.
+.SH "Installation and Configuration Improvements"
+.IX Header "Installation and Configuration Improvements"
+.SS "\-Dusethreads means something different"
+.IX Subsection "-Dusethreads means something different"
+The \-Dusethreads flag now enables the experimental interpreter-based thread
+support by default.  To get the flavor of experimental threads that was in
+5.005 instead, you need to run Configure with "\-Dusethreads \-Duse5005threads".
+.PP
+As of v5.6.0, interpreter-threads support is still lacking a way to
+create new threads from Perl (i.e., \f(CW\*(C`use Thread;\*(C'\fR will not work with
+interpreter threads).  \f(CW\*(C`use Thread;\*(C'\fR continues to be available when you
+specify the \-Duse5005threads option to Configure, bugs and all.
+.PP
+.Vb 2
+\&    NOTE: Support for threads continues to be an experimental feature.
+\&    Interfaces and implementation are subject to sudden and drastic changes.
+.Ve
+.SS "New Configure flags"
+.IX Subsection "New Configure flags"
+The following new flags may be enabled on the Configure command line
+by running Configure with \f(CW\*(C`\-Dflag\*(C'\fR.
+.PP
+.Vb 3
+\&    usemultiplicity
+\&    usethreads useithreads      (new interpreter threads: no Perl API yet)
+\&    usethreads use5005threads   (threads as they were in 5.005)
+\&
+\&    use64bitint                 (equal to now deprecated \*(Aquse64bits\*(Aq)
+\&    use64bitall
+\&
+\&    uselongdouble
+\&    usemorebits
+\&    uselargefiles
+\&    usesocks                    (only SOCKS v5 supported)
+.Ve
+.SS "Threadedness and 64\-bitness now more daring"
+.IX Subsection "Threadedness and 64-bitness now more daring"
+The Configure options enabling the use of threads and the use of
+64\-bitness are now more daring in the sense that they no more have an
+explicit list of operating systems of known threads/64\-bit
+capabilities.  In other words: if your operating system has the
+necessary APIs and datatypes, you should be able just to go ahead and
+use them, for threads by Configure \-Dusethreads, and for 64 bits
+either explicitly by Configure \-Duse64bitint or implicitly if your
+system has 64\-bit wide datatypes.  See also "64\-bit support".
+.SS "Long Doubles"
+.IX Subsection "Long Doubles"
+Some platforms have "long doubles", floating point numbers of even
+larger range than ordinary "doubles".  To enable using long doubles for
+Perl's scalars, use \-Duselongdouble.
+.SS \-Dusemorebits
+.IX Subsection "-Dusemorebits"
+You can enable both \-Duse64bitint and \-Duselongdouble with \-Dusemorebits.
+See also "64\-bit support".
+.SS \-Duselargefiles
+.IX Subsection "-Duselargefiles"
+Some platforms support system APIs that are capable of handling large files
+(typically, files larger than two gigabytes).  Perl will try to use these
+APIs if you ask for \-Duselargefiles.
+.PP
+See "Large file support" for more information.
+.SS installusrbinperl
+.IX Subsection "installusrbinperl"
+You can use "Configure \-Uinstallusrbinperl" which causes installperl
+to skip installing perl also as /usr/bin/perl.  This is useful if you
+prefer not to modify /usr/bin for some reason or another but harmful
+because many scripts assume to find Perl in /usr/bin/perl.
+.SS "SOCKS support"
+.IX Subsection "SOCKS support"
+You can use "Configure \-Dusesocks" which causes Perl to probe
+for the SOCKS proxy protocol library (v5, not v4).  For more information
+on SOCKS, see:
+.PP
+.Vb 1
+\&    http://www.socks.nec.com/
+.Ve
+.ie n .SS """\-A"" flag"
+.el .SS "\f(CW\-A\fP flag"
+.IX Subsection "-A flag"
+You can "post-edit" the Configure variables using the Configure \f(CW\*(C`\-A\*(C'\fR
+switch.  The editing happens immediately after the platform specific
+hints files have been processed but before the actual configuration
+process starts.  Run \f(CW\*(C`Configure \-h\*(C'\fR to find out the full \f(CW\*(C`\-A\*(C'\fR syntax.
+.SS "Enhanced Installation Directories"
+.IX Subsection "Enhanced Installation Directories"
+The installation structure has been enriched to improve the support
+for maintaining multiple versions of perl, to provide locations for
+vendor-supplied modules, scripts, and manpages, and to ease maintenance
+of locally-added modules, scripts, and manpages.  See the section on
+Installation Directories in the INSTALL file for complete details.
+For most users building and installing from source, the defaults should
+be fine.
+.PP
+If you previously used \f(CW\*(C`Configure \-Dsitelib\*(C'\fR or \f(CW\*(C`\-Dsitearch\*(C'\fR to set
+special values for library directories, you might wish to consider using
+the new \f(CW\*(C`\-Dsiteprefix\*(C'\fR setting instead.  Also, if you wish to re-use a
+config.sh file from an earlier version of perl, you should be sure to
+check that Configure makes sensible choices for the new directories.
+See INSTALL for complete details.
+.SH "Platform specific changes"
+.IX Header "Platform specific changes"
+.SS "Supported platforms"
+.IX Subsection "Supported platforms"
+.IP \(bu 4
+The Mach CThreads (NEXTSTEP, OPENSTEP) are now supported by the Thread
+extension.
+.IP \(bu 4
+GNU/Hurd is now supported.
+.IP \(bu 4
+Rhapsody/Darwin is now supported.
+.IP \(bu 4
+EPOC is now supported (on Psion 5).
+.IP \(bu 4
+The cygwin port (formerly cygwin32) has been greatly improved.
+.SS DOS
+.IX Subsection "DOS"
+.IP \(bu 4
+Perl now works with djgpp 2.02 (and 2.03 alpha).
+.IP \(bu 4
+Environment variable names are not converted to uppercase any more.
+.IP \(bu 4
+Incorrect exit codes from backticks have been fixed.
+.IP \(bu 4
+This port continues to use its own builtin globbing (not File::Glob).
+.SS "OS390 (OpenEdition MVS)"
+.IX Subsection "OS390 (OpenEdition MVS)"
+Support for this EBCDIC platform has not been renewed in this release.
+There are difficulties in reconciling Perl's standardization on UTF\-8
+as its internal representation for characters with the EBCDIC character
+set, because the two are incompatible.
+.PP
+It is unclear whether future versions will renew support for this
+platform, but the possibility exists.
+.SS VMS
+.IX Subsection "VMS"
+Numerous revisions and extensions to configuration, build, testing, and
+installation process to accommodate core changes and VMS-specific options.
+.PP
+Expand \f(CW%ENV\fR\-handling code to allow runtime mapping to logical names,
+CLI symbols, and CRTL environ array.
+.PP
+Extension of subprocess invocation code to accept filespecs as command
+"verbs".
+.PP
+Add to Perl command line processing the ability to use default file types and
+to recognize Unix-style \f(CW\*(C`2>&1\*(C'\fR.
+.PP
+Expansion of File::Spec::VMS routines, and integration into ExtUtils::MM_VMS.
+.PP
+Extension of ExtUtils::MM_VMS to handle complex extensions more flexibly.
+.PP
+Barewords at start of Unix-syntax paths may be treated as text rather than
+only as logical names.
+.PP
+Optional secure translation of several logical names used internally by Perl.
+.PP
+Miscellaneous bugfixing and porting of new core code to VMS.
+.PP
+Thanks are gladly extended to the many people who have contributed VMS
+patches, testing, and ideas.
+.SS Win32
+.IX Subsection "Win32"
+Perl can now emulate \fBfork()\fR internally, using multiple interpreters running
+in different concurrent threads.  This support must be enabled at build
+time.  See perlfork for detailed information.
+.PP
+When given a pathname that consists only of a drivename, such as \f(CW\*(C`A:\*(C'\fR,
+\&\fBopendir()\fR and \fBstat()\fR now use the current working directory for the drive
+rather than the drive root.
+.PP
+The builtin XSUB functions in the Win32:: namespace are documented.  See
+Win32.
+.PP
+$^X now contains the full path name of the running executable.
+.PP
+A \fBWin32::GetLongPathName()\fR function is provided to complement
+\&\fBWin32::GetFullPathName()\fR and \fBWin32::GetShortPathName()\fR.  See Win32.
+.PP
+\&\fBPOSIX::uname()\fR is supported.
+.PP
+system(1,...) now returns true process IDs rather than process
+handles.  \fBkill()\fR accepts any real process id, rather than strictly
+return values from system(1,...).
+.PP
+For better compatibility with Unix, \f(CW\*(C`kill(0, $pid)\*(C'\fR can now be used to
+test whether a process exists.
+.PP
+The \f(CW\*(C`Shell\*(C'\fR module is supported.
+.PP
+Better support for building Perl under command.com in Windows 95
+has been added.
+.PP
+Scripts are read in binary mode by default to allow ByteLoader (and
+the filter mechanism in general) to work properly.  For compatibility,
+the DATA filehandle will be set to text mode if a carriage return is
+detected at the end of the line containing the _\|_END_\|_ or _\|_DATA_\|_
+token; if not, the DATA filehandle will be left open in binary mode.
+Earlier versions always opened the DATA filehandle in text mode.
+.PP
+The \fBglob()\fR operator is implemented via the \f(CW\*(C`File::Glob\*(C'\fR extension,
+which supports glob syntax of the C shell.  This increases the flexibility
+of the \fBglob()\fR operator, but there may be compatibility issues for
+programs that relied on the older globbing syntax.  If you want to
+preserve compatibility with the older syntax, you might want to run
+perl with \f(CW\*(C`\-MFile::DosGlob\*(C'\fR.  For details and compatibility information,
+see File::Glob.
+.SH "Significant bug fixes"
+.IX Header "Significant bug fixes"
+.SS "<HANDLE> on empty files"
+.IX Subsection "<HANDLE> on empty files"
+With \f(CW$/\fR set to \f(CW\*(C`undef\*(C'\fR, "slurping" an empty file returns a string of
+zero length (instead of \f(CW\*(C`undef\*(C'\fR, as it used to) the first time the
+HANDLE is read after \f(CW$/\fR is set to \f(CW\*(C`undef\*(C'\fR.  Further reads yield
+\&\f(CW\*(C`undef\*(C'\fR.
+.PP
+This means that the following will append "foo" to an empty file (it used
+to do nothing):
+.PP
+.Vb 1
+\&    perl \-0777 \-pi \-e \*(Aqs/^/foo/\*(Aq empty_file
+.Ve
+.PP
+The behaviour of:
+.PP
+.Vb 1
+\&    perl \-pi \-e \*(Aqs/^/foo/\*(Aq empty_file
+.Ve
+.PP
+is unchanged (it continues to leave the file empty).
+.ie n .SS """eval \*(Aq...\*(Aq"" improvements"
+.el .SS "\f(CWeval \*(Aq...\*(Aq\fP improvements"
+.IX Subsection "eval ... improvements"
+Line numbers (as reflected by \fBcaller()\fR and most diagnostics) within
+\&\f(CW\*(C`eval \*(Aq...\*(Aq\*(C'\fR were often incorrect where here documents were involved.
+This has been corrected.
+.PP
+Lexical lookups for variables appearing in \f(CW\*(C`eval \*(Aq...\*(Aq\*(C'\fR within
+functions that were themselves called within an \f(CW\*(C`eval \*(Aq...\*(Aq\*(C'\fR were
+searching the wrong place for lexicals.  The lexical search now
+correctly ends at the subroutine's block boundary.
+.PP
+The use of \f(CW\*(C`return\*(C'\fR within \f(CW\*(C`eval {...}\*(C'\fR caused $@ not to be reset
+correctly when no exception occurred within the eval.  This has
+been fixed.
+.PP
+Parsing of here documents used to be flawed when they appeared as
+the replacement expression in \f(CW\*(C`eval \*(Aqs/.../.../e\*(Aq\*(C'\fR.  This has
+been fixed.
+.SS "All compilation errors are true errors"
+.IX Subsection "All compilation errors are true errors"
+Some "errors" encountered at compile time were by necessity 
+generated as warnings followed by eventual termination of the
+program.  This enabled more such errors to be reported in a
+single run, rather than causing a hard stop at the first error
+that was encountered.
+.PP
+The mechanism for reporting such errors has been reimplemented
+to queue compile-time errors and report them at the end of the
+compilation as true errors rather than as warnings.  This fixes
+cases where error messages leaked through in the form of warnings
+when code was compiled at run time using \f(CW\*(C`eval STRING\*(C'\fR, and
+also allows such errors to be reliably trapped using \f(CW\*(C`eval "..."\*(C'\fR.
+.SS "Implicitly closed filehandles are safer"
+.IX Subsection "Implicitly closed filehandles are safer"
+Sometimes implicitly closed filehandles (as when they are localized,
+and Perl automatically closes them on exiting the scope) could
+inadvertently set $? or $!.  This has been corrected.
+.SS "Behavior of list slices is more consistent"
+.IX Subsection "Behavior of list slices is more consistent"
+When taking a slice of a literal list (as opposed to a slice of
+an array or hash), Perl used to return an empty list if the
+result happened to be composed of all undef values.
+.PP
+The new behavior is to produce an empty list if (and only if)
+the original list was empty.  Consider the following example:
+.PP
+.Vb 1
+\&    @a = (1,undef,undef,2)[2,1,2];
+.Ve
+.PP
+The old behavior would have resulted in \f(CW@a\fR having no elements.
+The new behavior ensures it has three undefined elements.
+.PP
+Note in particular that the behavior of slices of the following
+cases remains unchanged:
+.PP
+.Vb 5
+\&    @a = ()[1,2];
+\&    @a = (getpwent)[7,0];
+\&    @a = (anything_returning_empty_list())[2,1,2];
+\&    @a = @b[2,1,2];
+\&    @a = @c{\*(Aqa\*(Aq,\*(Aqb\*(Aq,\*(Aqc\*(Aq};
+.Ve
+.PP
+See perldata.
+.ie n .SS """(\e$)"" prototype and $foo{a}"
+.el .SS "\f(CW(\e$)\fP prototype and \f(CW$foo{a}\fP"
+.IX Subsection "($) prototype and $foo{a}"
+A scalar reference prototype now correctly allows a hash or
+array element in that slot.
+.ie n .SS """goto &sub"" and AUTOLOAD"
+.el .SS "\f(CWgoto &sub\fP and AUTOLOAD"
+.IX Subsection "goto &sub and AUTOLOAD"
+The \f(CW\*(C`goto &sub\*(C'\fR construct works correctly when \f(CW&sub\fR happens
+to be autoloaded.
+.ie n .SS """\-bareword"" allowed under ""use integer"""
+.el .SS "\f(CW\-bareword\fP allowed under \f(CWuse integer\fP"
+.IX Subsection "-bareword allowed under use integer"
+The autoquoting of barewords preceded by \f(CW\*(C`\-\*(C'\fR did not work
+in prior versions when the \f(CW\*(C`integer\*(C'\fR pragma was enabled.
+This has been fixed.
+.SS "Failures in \fBDESTROY()\fP"
+.IX Subsection "Failures in DESTROY()"
+When code in a destructor threw an exception, it went unnoticed
+in earlier versions of Perl, unless someone happened to be
+looking in $@ just after the point the destructor happened to
+run.  Such failures are now visible as warnings when warnings are
+enabled.
+.SS "Locale bugs fixed"
+.IX Subsection "Locale bugs fixed"
+\&\fBprintf()\fR and \fBsprintf()\fR previously reset the numeric locale
+back to the default "C" locale.  This has been fixed.
+.PP
+Numbers formatted according to the local numeric locale
+(such as using a decimal comma instead of a decimal dot) caused
+"isn't numeric" warnings, even while the operations accessing
+those numbers produced correct results.  These warnings have been
+discontinued.
+.SS "Memory leaks"
+.IX Subsection "Memory leaks"
+The \f(CW\*(C`eval \*(Aqreturn sub {...}\*(Aq\*(C'\fR construct could sometimes leak
+memory.  This has been fixed.
+.PP
+Operations that aren't filehandle constructors used to leak memory
+when used on invalid filehandles.  This has been fixed.
+.PP
+Constructs that modified \f(CW@_\fR could fail to deallocate values
+in \f(CW@_\fR and thus leak memory.  This has been corrected.
+.SS "Spurious subroutine stubs after failed subroutine calls"
+.IX Subsection "Spurious subroutine stubs after failed subroutine calls"
+Perl could sometimes create empty subroutine stubs when a
+subroutine was not found in the package.  Such cases stopped
+later method lookups from progressing into base packages.
+This has been corrected.
+.ie n .SS "Taint failures under ""\-U"""
+.el .SS "Taint failures under \f(CW\-U\fP"
+.IX Subsection "Taint failures under -U"
+When running in unsafe mode, taint violations could sometimes
+cause silent failures.  This has been fixed.
+.ie n .SS "END blocks and the ""\-c"" switch"
+.el .SS "END blocks and the \f(CW\-c\fP switch"
+.IX Subsection "END blocks and the -c switch"
+Prior versions used to run BEGIN \fBand\fR END blocks when Perl was
+run in compile-only mode.  Since this is typically not the expected
+behavior, END blocks are not executed anymore when the \f(CW\*(C`\-c\*(C'\fR switch
+is used, or if compilation fails.
+.PP
+See "Support for CHECK blocks" for how to run things when the compile 
+phase ends.
+.SS "Potential to leak DATA filehandles"
+.IX Subsection "Potential to leak DATA filehandles"
+Using the \f(CW\*(C`_\|_DATA_\|_\*(C'\fR token creates an implicit filehandle to
+the file that contains the token.  It is the program's
+responsibility to close it when it is done reading from it.
+.PP
+This caveat is now better explained in the documentation.
+See perldata.
+.SH "New or Changed Diagnostics"
+.IX Header "New or Changed Diagnostics"
+.ie n .IP """%s"" variable %s masks earlier declaration in same %s" 4
+.el .IP """%s"" variable \f(CW%s\fR masks earlier declaration in same \f(CW%s\fR" 4
+.IX Item """%s"" variable %s masks earlier declaration in same %s"
+(W misc) A "my" or "our" variable 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 variable will still exist
+until the end of the scope or until all closure referents to it are
+destroyed.
+.IP """my sub"" not yet implemented" 4
+.IX Item """my sub"" not yet implemented"
+(F) Lexically scoped subroutines are not yet implemented.  Don't try that
+yet.
+.ie n .IP """our"" variable %s redeclared" 4
+.el .IP """our"" variable \f(CW%s\fR redeclared" 4
+.IX Item """our"" variable %s redeclared"
+(W misc) You seem to have already declared the same global once before in the
+current lexical scope.
+.ie n .IP "'!' allowed only after types %s" 4
+.el .IP "'!' allowed only after types \f(CW%s\fR" 4
+.IX Item "'!' allowed only after types %s"
+(F) The '!' is allowed in \fBpack()\fR and \fBunpack()\fR only after certain types.
+See "pack" in perlfunc.
+.IP "/ cannot take a count" 4
+.IX Item "/ cannot take a count"
+(F) You had an unpack template indicating a counted-length string,
+but you have also specified an explicit size for the string.
+See "pack" in perlfunc.
+.IP "/ must be followed by a, A or Z" 4
+.IX Item "/ must be followed by a, A or Z"
+(F) You had an unpack template indicating a counted-length string,
+which must be followed by one of the letters a, A or Z
+to indicate what sort of string is to be unpacked.
+See "pack" in perlfunc.
+.IP "/ must be followed by a*, A* or Z*" 4
+.IX Item "/ must be followed by a*, A* or Z*"
+(F) You had a pack template indicating a counted-length string,
+Currently the only things that can have their length counted are a*, A* or Z*.
+See "pack" in perlfunc.
+.IP "/ must follow a numeric type" 4
+.IX Item "/ must follow a numeric type"
+(F) You had an unpack template that contained a '#',
+but this did not follow some numeric unpack specification.
+See "pack" in perlfunc.
+.IP "/%s/: Unrecognized escape \e\e%c passed through" 4
+.IX Item "/%s/: Unrecognized escape %c passed through"
+(W regexp) You used a backslash-character combination which is not recognized
+by Perl.  This combination appears in an interpolated variable or a
+\&\f(CW\*(C`\*(Aq\*(C'\fR\-delimited regular expression.  The character was understood literally.
+.IP "/%s/: Unrecognized escape \e\e%c in character class passed through" 4
+.IX Item "/%s/: Unrecognized escape %c in character class passed through"
+(W regexp) You used a backslash-character combination which is not recognized
+by Perl inside character classes.  The character was understood literally.
+.IP "/%s/ should probably be written as ""%s""" 4
+.IX Item "/%s/ should probably be written as ""%s"""
+(W syntax) You have used a pattern where Perl expected to find a string,
+as in the first argument to \f(CW\*(C`join\*(C'\fR.  Perl will treat the true
+or false result of matching the pattern against \f(CW$_\fR as the string,
+which is probably not what you had in mind.
+.IP "%s() called too early to check prototype" 4
+.IX Item "%s() called too early to check prototype"
+(W prototype) You've called a function that has a prototype before the parser saw a
+definition or declaration for it, and Perl could not check that the call
+conforms to the prototype.  You need to either add an early prototype
+declaration for the subroutine in question, or move the subroutine
+definition ahead of the call to get proper prototype checking.  Alternatively,
+if you are certain that you're calling the function correctly, you may put
+an ampersand before the name to avoid the warning.  See perlsub.
+.ie n .IP "%s argument is not a HASH or ARRAY element" 4
+.el .IP "\f(CW%s\fR argument is not a HASH or ARRAY element" 4
+.IX Item "%s argument is not a HASH or ARRAY element"
+(F) The argument to \fBexists()\fR must be a hash or array element, such as:
+.Sp
+.Vb 2
+\&    $foo{$bar}
+\&    $ref\->{"susie"}[12]
+.Ve
+.ie n .IP "%s argument is not a HASH or ARRAY element or slice" 4
+.el .IP "\f(CW%s\fR argument is not a HASH or ARRAY element or slice" 4
+.IX Item "%s argument is not a HASH or ARRAY element or slice"
+(F) The argument to \fBdelete()\fR must be either a hash or array element, such as:
+.Sp
+.Vb 2
+\&    $foo{$bar}
+\&    $ref\->{"susie"}[12]
+.Ve
+.Sp
+or a hash or array slice, such as:
+.Sp
+.Vb 2
+\&    @foo[$bar, $baz, $xyzzy]
+\&    @{$ref\->[12]}{"susie", "queue"}
+.Ve
+.ie n .IP "%s argument is not a subroutine name" 4
+.el .IP "\f(CW%s\fR argument is not a subroutine name" 4
+.IX Item "%s argument is not a subroutine name"
+(F) The argument to \fBexists()\fR for \f(CW\*(C`exists &sub\*(C'\fR must be a subroutine
+name, and not a subroutine call.  \f(CW\*(C`exists &sub()\*(C'\fR will generate this error.
+.ie n .IP "%s package attribute may clash with future reserved word: %s" 4
+.el .IP "\f(CW%s\fR package attribute may clash with future reserved word: \f(CW%s\fR" 4
+.IX Item "%s package attribute may clash with future reserved word: %s"
+(W reserved) A lowercase attribute name was used that had a package-specific handler.
+That name might have a meaning to Perl itself some day, even though it
+doesn't yet.  Perhaps you should use a mixed-case attribute name, instead.
+See attributes.
+.ie n .IP "(in cleanup) %s" 4
+.el .IP "(in cleanup) \f(CW%s\fR" 4
+.IX Item "(in cleanup) %s"
+(W misc) This prefix usually indicates that a \fBDESTROY()\fR method raised
+the indicated exception.  Since destructors are usually called by
+the system at arbitrary points during execution, and often a vast
+number of times, the warning is issued only once for any number
+of failures that would otherwise result in the same message being
+repeated.
+.Sp
+Failure of user callbacks dispatched using the \f(CW\*(C`G_KEEPERR\*(C'\fR flag
+could also result in this warning.  See "G_KEEPERR" in perlcall.
+.IP "<> should be quotes" 4
+.IX Item "<> should be quotes"
+(F) You wrote \f(CW\*(C`require <file>\*(C'\fR when you should have written
+\&\f(CW\*(C`require \*(Aqfile\*(Aq\*(C'\fR.
+.IP "Attempt to join self" 4
+.IX Item "Attempt to join self"
+(F) You tried to join a thread from within itself, which is an
+impossible task.  You may be joining the wrong thread, or you may
+need to move the \fBjoin()\fR to some other thread.
+.IP "Bad evalled substitution pattern" 4
+.IX Item "Bad evalled substitution pattern"
+(F) You've used the /e switch to evaluate the replacement for a
+substitution, but perl found a syntax error in the code to evaluate,
+most likely an unexpected right brace '}'.
+.IP "Bad \fBrealloc()\fR ignored" 4
+.IX Item "Bad realloc() ignored"
+(S) An internal routine called \fBrealloc()\fR on something that had never been
+\&\fBmalloc()\fRed in the first place. Mandatory, but can be disabled by
+setting environment variable \f(CW\*(C`PERL_BADFREE\*(C'\fR to 1.
+.IP "Bareword found in conditional" 4
+.IX Item "Bareword found in conditional"
+(W bareword) The compiler found a bareword where it expected a conditional,
+which often indicates that an || or && was parsed as part of the
+last argument of the previous construct, for example:
+.Sp
+.Vb 1
+\&    open FOO || die;
+.Ve
+.Sp
+It may also indicate a misspelled constant that has been interpreted
+as a bareword:
+.Sp
+.Vb 2
+\&    use constant TYPO => 1;
+\&    if (TYOP) { print "foo" }
+.Ve
+.Sp
+The \f(CW\*(C`strict\*(C'\fR pragma is useful in avoiding such errors.
+.IP "Binary number > 0b11111111111111111111111111111111 non-portable" 4
+.IX Item "Binary number > 0b11111111111111111111111111111111 non-portable"
+(W portable) The binary number you specified is larger than 2**32\-1
+(4294967295) and therefore non-portable between systems.  See
+perlport for more on portability concerns.
+.IP "Bit vector size > 32 non-portable" 4
+.IX Item "Bit vector size > 32 non-portable"
+(W portable) Using bit vector sizes larger than 32 is non-portable.
+.ie n .IP "Buffer overflow in prime_env_iter: %s" 4
+.el .IP "Buffer overflow in prime_env_iter: \f(CW%s\fR" 4
+.IX Item "Buffer overflow in prime_env_iter: %s"
+(W internal) A warning peculiar to VMS.  While Perl was preparing to iterate over
+\&\f(CW%ENV\fR, it encountered a logical name or symbol definition which was too long,
+so it was truncated to the string shown.
+.IP "Can't check filesystem of script ""%s""" 4
+.IX Item "Can't check filesystem of script ""%s"""
+(P) For some reason you can't check the filesystem of the script for nosuid.
+.ie n .IP "Can't declare class for non-scalar %s in ""%s""" 4
+.el .IP "Can't declare class for non-scalar \f(CW%s\fR in ""%s""" 4
+.IX Item "Can't declare class for non-scalar %s in ""%s"""
+(S) Currently, only scalar variables can declared with a specific class
+qualifier in a "my" or "our" declaration.  The semantics may be extended
+for other types of variables in future.
+.ie n .IP "Can't declare %s in ""%s""" 4
+.el .IP "Can't declare \f(CW%s\fR in ""%s""" 4
+.IX Item "Can't declare %s in ""%s"""
+(F) Only scalar, array, and hash variables may be declared as "my" or
+"our" variables.  They must have ordinary identifiers as names.
+.IP "Can't ignore signal CHLD, forcing to default" 4
+.IX Item "Can't ignore signal CHLD, forcing to default"
+(W signal) Perl has detected that it is being run with the SIGCHLD signal
+(sometimes known as SIGCLD) disabled.  Since disabling this signal
+will interfere with proper determination of exit status of child
+processes, Perl has reset the signal to its default value.
+This situation typically indicates that the parent program under
+which Perl may be running (e.g., cron) is being very careless.
+.IP "Can't modify non-lvalue subroutine call" 4
+.IX Item "Can't modify non-lvalue subroutine call"
+(F) Subroutines meant to be used in lvalue context should be declared as
+such, see "Lvalue subroutines" in perlsub.
+.IP "Can't read CRTL environ" 4
+.IX Item "Can't read CRTL environ"
+(S) A warning peculiar to VMS.  Perl tried to read an element of \f(CW%ENV\fR
+from the CRTL's internal environment array and discovered the array was
+missing.  You need to figure out where your CRTL misplaced its environ
+or define \fIPERL_ENV_TABLES\fR (see perlvms) so that environ is not searched.
+.ie n .IP "Can't remove %s: %s, skipping file" 4
+.el .IP "Can't remove \f(CW%s:\fR \f(CW%s\fR, skipping file" 4
+.IX Item "Can't remove %s: %s, skipping file"
+(S) You requested an inplace edit without creating a backup file.  Perl
+was unable to remove the original file to replace it with the modified
+file.  The file was left unmodified.
+.ie n .IP "Can't return %s from lvalue subroutine" 4
+.el .IP "Can't return \f(CW%s\fR from lvalue subroutine" 4
+.IX Item "Can't return %s from lvalue subroutine"
+(F) Perl detected an attempt to return illegal lvalues (such
+as temporary or readonly values) from a subroutine used as an lvalue.
+This is not allowed.
+.IP "Can't weaken a nonreference" 4
+.IX Item "Can't weaken a nonreference"
+(F) You attempted to weaken something that was not a reference.  Only
+references can be weakened.
+.IP "Character class [:%s:] unknown" 4
+.IX Item "Character class [:%s:] unknown"
+(F) The class in the character class [: :] syntax is unknown.
+See perlre.
+.IP "Character class syntax [%s] belongs inside character classes" 4
+.IX Item "Character class syntax [%s] belongs inside character classes"
+(W unsafe) The character class constructs [: :], [= =], and [. .]  go
+\&\fIinside\fR character classes, the [] are part of the construct,
+for example: /[012[:alpha:]345]/.  Note that [= =] and [. .]
+are not currently implemented; they are simply placeholders for
+future extensions.
+.ie n .IP "Constant is not %s reference" 4
+.el .IP "Constant is not \f(CW%s\fR reference" 4
+.IX Item "Constant is not %s reference"
+(F) A constant value (perhaps declared using the \f(CW\*(C`use constant\*(C'\fR pragma)
+is being dereferenced, but it amounts to the wrong type of reference.  The
+message indicates the type of reference that was expected. This usually
+indicates a syntax error in dereferencing the constant value.
+See "Constant Functions" in perlsub and constant.
+.ie n .IP "constant(%s): %s" 4
+.el .IP "constant(%s): \f(CW%s\fR" 4
+.IX Item "constant(%s): %s"
+(F) The parser found inconsistencies either while attempting to define an
+overloaded constant, or when trying to find the character name specified
+in the \f(CW\*(C`\eN{...}\*(C'\fR escape.  Perhaps you forgot to load the corresponding
+\&\f(CW\*(C`overload\*(C'\fR or \f(CW\*(C`charnames\*(C'\fR pragma?  See charnames and overload.
+.IP "CORE::%s is not a keyword" 4
+.IX Item "CORE::%s is not a keyword"
+(F) The CORE:: namespace is reserved for Perl keywords.
+.IP "defined(@array) is deprecated" 4
+.IX Item "defined(@array) is deprecated"
+(D) \fBdefined()\fR is not usually useful on arrays because it checks for an
+undefined \fIscalar\fR value.  If you want to see if the array is empty,
+just use \f(CW\*(C`if (@array) { # not empty }\*(C'\fR for example.
+.IP "defined(%hash) is deprecated" 4
+.IX Item "defined(%hash) is deprecated"
+(D) \fBdefined()\fR is not usually useful on hashes because it checks for an
+undefined \fIscalar\fR value.  If you want to see if the hash is empty,
+just use \f(CW\*(C`if (%hash) { # not empty }\*(C'\fR for example.
+.IP "Did not produce a valid header" 4
+.IX Item "Did not produce a valid header"
+See Server error.
+.IP "(Did you mean ""local"" instead of ""our""?)" 4
+.IX Item "(Did you mean ""local"" instead of ""our""?)"
+(W misc) Remember that "our" does not localize the declared global variable.
+You have declared it again in the same lexical scope, which seems superfluous.
+.IP "Document contains no data" 4
+.IX Item "Document contains no data"
+See Server error.
+.ie n .IP "entering effective %s failed" 4
+.el .IP "entering effective \f(CW%s\fR failed" 4
+.IX Item "entering effective %s failed"
+(F) While under the \f(CW\*(C`use filetest\*(C'\fR pragma, switching the real and
+effective uids or gids failed.
+.IP "false [] range ""%s"" in regexp" 4
+.IX Item "false [] range ""%s"" in regexp"
+(W regexp) A character class range must start and end at a literal character, not
+another character class like \f(CW\*(C`\ed\*(C'\fR or \f(CW\*(C`[:alpha:]\*(C'\fR.  The "\-" in your false
+range is interpreted as a literal "\-".  Consider quoting the "\-",  "\e\-".
+See perlre.
+.ie n .IP "Filehandle %s opened only for output" 4
+.el .IP "Filehandle \f(CW%s\fR opened only for output" 4
+.IX Item "Filehandle %s opened only for output"
+(W io) You tried to read from a filehandle opened only for writing.  If you
+intended it to be a read/write filehandle, you needed to open it with
+"+<" or "+>" or "+>>" instead of with "<" or nothing.  If
+you intended only to read from the file, use "<".  See
+"open" in perlfunc.
+.ie n .IP "\fBflock()\fR on closed filehandle %s" 4
+.el .IP "\fBflock()\fR on closed filehandle \f(CW%s\fR" 4
+.IX Item "flock() on closed filehandle %s"
+(W closed) The filehandle you're attempting to \fBflock()\fR got itself closed some
+time before now.  Check your logic flow.  \fBflock()\fR operates on filehandles.
+Are you attempting to call \fBflock()\fR on a dirhandle by the same name?
+.IP "Global symbol ""%s"" requires explicit package name" 4
+.IX Item "Global symbol ""%s"" requires explicit package name"
+(F) You've said "use strict vars", which indicates that all variables
+must either be lexically scoped (using "my"), declared beforehand using
+"our", or explicitly qualified to say which package the global variable
+is in (using "::").
+.IP "Hexadecimal number > 0xffffffff non-portable" 4
+.IX Item "Hexadecimal number > 0xffffffff non-portable"
+(W portable) The hexadecimal number you specified is larger than 2**32\-1
+(4294967295) and therefore non-portable between systems.  See
+perlport for more on portability concerns.
+.IP "Ill-formed CRTL environ value ""%s""" 4
+.IX Item "Ill-formed CRTL environ value ""%s"""
+(W internal) A warning peculiar to VMS.  Perl tried to read the CRTL's internal
+environ array, and encountered an element without the \f(CW\*(C`=\*(C'\fR delimiter
+used to separate keys from values.  The element is ignored.
+.IP "Ill-formed message in prime_env_iter: |%s|" 4
+.IX Item "Ill-formed message in prime_env_iter: |%s|"
+(W internal) A warning peculiar to VMS.  Perl tried to read a logical name
+or CLI symbol definition when preparing to iterate over \f(CW%ENV\fR, and
+didn't see the expected delimiter between key and value, so the
+line was ignored.
+.ie n .IP "Illegal binary digit %s" 4
+.el .IP "Illegal binary digit \f(CW%s\fR" 4
+.IX Item "Illegal binary digit %s"
+(F) You used a digit other than 0 or 1 in a binary number.
+.ie n .IP "Illegal binary digit %s ignored" 4
+.el .IP "Illegal binary digit \f(CW%s\fR ignored" 4
+.IX Item "Illegal binary digit %s ignored"
+(W digit) You may have tried to use a digit other than 0 or 1 in a binary number.
+Interpretation of the binary number stopped before the offending digit.
+.IP "Illegal number of bits in vec" 4
+.IX Item "Illegal number of bits in vec"
+(F) The number of bits in \fBvec()\fR (the third argument) must be a power of
+two from 1 to 32 (or 64, if your platform supports that).
+.ie n .IP "Integer overflow in %s number" 4
+.el .IP "Integer overflow in \f(CW%s\fR number" 4
+.IX Item "Integer overflow in %s number"
+(W overflow) The hexadecimal, octal or binary number you have specified either
+as a literal or as an argument to \fBhex()\fR or \fBoct()\fR is too big for your
+architecture, and has been converted to a floating point number.  On a
+32\-bit architecture the largest hexadecimal, octal or binary number
+representable without overflow is 0xFFFFFFFF, 037777777777, or
+0b11111111111111111111111111111111 respectively.  Note that Perl
+transparently promotes all numbers to a floating point representation
+internally\-\-subject to loss of precision errors in subsequent
+operations.
+.ie n .IP "Invalid %s attribute: %s" 4
+.el .IP "Invalid \f(CW%s\fR attribute: \f(CW%s\fR" 4
+.IX Item "Invalid %s attribute: %s"
+The indicated attribute for a subroutine or variable was not recognized
+by Perl or by a user-supplied handler.  See attributes.
+.ie n .IP "Invalid %s attributes: %s" 4
+.el .IP "Invalid \f(CW%s\fR attributes: \f(CW%s\fR" 4
+.IX Item "Invalid %s attributes: %s"
+The indicated attributes for a subroutine or variable were not recognized
+by Perl or by a user-supplied handler.  See attributes.
+.IP "invalid [] range ""%s"" in regexp" 4
+.IX Item "invalid [] range ""%s"" in regexp"
+The offending range is now explicitly displayed.
+.ie n .IP "Invalid separator character %s in attribute list" 4
+.el .IP "Invalid separator character \f(CW%s\fR in attribute list" 4
+.IX Item "Invalid separator character %s in attribute list"
+(F) Something other than a colon or whitespace was seen between the
+elements of an attribute list.  If the previous attribute
+had a parenthesised parameter list, perhaps that list was terminated
+too soon.  See attributes.
+.ie n .IP "Invalid separator character %s in subroutine attribute list" 4
+.el .IP "Invalid separator character \f(CW%s\fR in subroutine attribute list" 4
+.IX Item "Invalid separator character %s in subroutine attribute list"
+(F) Something other than a colon or whitespace was seen between the
+elements of a subroutine attribute list.  If the previous attribute
+had a parenthesised parameter list, perhaps that list was terminated
+too soon.
+.ie n .IP "leaving effective %s failed" 4
+.el .IP "leaving effective \f(CW%s\fR failed" 4
+.IX Item "leaving effective %s failed"
+(F) While under the \f(CW\*(C`use filetest\*(C'\fR pragma, switching the real and
+effective uids or gids failed.
+.ie n .IP "Lvalue subs returning %s not implemented yet" 4
+.el .IP "Lvalue subs returning \f(CW%s\fR not implemented yet" 4
+.IX Item "Lvalue subs returning %s not implemented yet"
+(F) Due to limitations in the current implementation, array and hash
+values cannot be returned in subroutines used in lvalue context.
+See "Lvalue subroutines" in perlsub.
+.ie n .IP "Method %s not permitted" 4
+.el .IP "Method \f(CW%s\fR not permitted" 4
+.IX Item "Method %s not permitted"
+See Server error.
+.ie n .IP "Missing %sbrace%s on \eN{}" 4
+.el .IP "Missing \f(CW%sbrace\fR%s on \eN{}" 4
+.IX Item "Missing %sbrace%s on N{}"
+(F) Wrong syntax of character name literal \f(CW\*(C`\eN{charname}\*(C'\fR within
+double-quotish context.
+.IP "Missing command in piped open" 4
+.IX Item "Missing command in piped open"
+(W pipe) You used the \f(CW\*(C`open(FH, "| command")\*(C'\fR or \f(CW\*(C`open(FH, "command |")\*(C'\fR
+construction, but the command was missing or blank.
+.IP "Missing name in ""my sub""" 4
+.IX Item "Missing name in ""my sub"""
+(F) The reserved syntax for lexically scoped subroutines requires that they
+have a name with which they can be found.
+.ie n .IP "No %s specified for \-%c" 4
+.el .IP "No \f(CW%s\fR specified for \-%c" 4
+.IX Item "No %s specified for -%c"
+(F) The indicated command line switch needs a mandatory argument, but
+you haven't specified one.
+.ie n .IP "No package name allowed for variable %s in ""our""" 4
+.el .IP "No package name allowed for variable \f(CW%s\fR in ""our""" 4
+.IX Item "No package name allowed for variable %s in ""our"""
+(F) Fully qualified variable names are not allowed in "our" declarations,
+because that doesn't make much sense under existing semantics.  Such
+syntax is reserved for future extensions.
+.IP "No space allowed after \-%c" 4
+.IX Item "No space allowed after -%c"
+(F) The argument to the indicated command line switch must follow immediately
+after the switch, without intervening spaces.
+.IP "no UTC offset information; assuming local time is UTC" 4
+.IX Item "no UTC offset information; assuming local time is UTC"
+(S) A warning peculiar to VMS.  Perl was unable to find the local
+timezone offset, so it's assuming that local system time is equivalent
+to UTC.  If it's not, define the logical name \fISYS$TIMEZONE_DIFFERENTIAL\fR
+to translate to the number of seconds which need to be added to UTC to
+get local time.
+.IP "Octal number > 037777777777 non-portable" 4
+.IX Item "Octal number > 037777777777 non-portable"
+(W portable) The octal number you specified is larger than 2**32\-1 (4294967295)
+and therefore non-portable between systems.  See perlport for more
+on portability concerns.
+.Sp
+See also perlport for writing portable code.
+.IP "panic: del_backref" 4
+.IX Item "panic: del_backref"
+(P) Failed an internal consistency check while trying to reset a weak
+reference.
+.IP "panic: kid popen errno read" 4
+.IX Item "panic: kid popen errno read"
+(F) forked child returned an incomprehensible message about its errno.
+.IP "panic: magic_killbackrefs" 4
+.IX Item "panic: magic_killbackrefs"
+(P) Failed an internal consistency check while trying to reset all weak
+references to an object.
+.IP "Parentheses missing around ""%s"" list" 4
+.IX Item "Parentheses missing around ""%s"" list"
+(W parenthesis) You said something like
+.Sp
+.Vb 1
+\&    my $foo, $bar = @_;
+.Ve
+.Sp
+when you meant
+.Sp
+.Vb 1
+\&    my ($foo, $bar) = @_;
+.Ve
+.Sp
+Remember that "my", "our", and "local" bind tighter than comma.
+.ie n .IP "Possible unintended interpolation of %s in string" 4
+.el .IP "Possible unintended interpolation of \f(CW%s\fR in string" 4
+.IX Item "Possible unintended interpolation of %s in string"
+(W ambiguous) It used to be that Perl would try to guess whether you
+wanted an array interpolated or a literal @.  It no longer does this;
+arrays are now \fIalways\fR interpolated into strings.  This means that 
+if you try something like:
+.Sp
+.Vb 1
+\&        print "fred@example.com";
+.Ve
+.Sp
+and the array \f(CW@example\fR doesn't exist, Perl is going to print
+\&\f(CW\*(C`fred.com\*(C'\fR, which is probably not what you wanted.  To get a literal
+\&\f(CW\*(C`@\*(C'\fR sign in a string, put a backslash before it, just as you would
+to get a literal \f(CW\*(C`$\*(C'\fR sign.
+.ie n .IP "Possible Y2K bug: %s" 4
+.el .IP "Possible Y2K bug: \f(CW%s\fR" 4
+.IX Item "Possible Y2K bug: %s"
+(W y2k) You are concatenating the number 19 with another number, which
+could be a potential Year 2000 problem.
+.IP "pragma ""attrs"" is deprecated, use ""sub NAME : ATTRS"" instead" 4
+.IX Item "pragma ""attrs"" is deprecated, use ""sub NAME : ATTRS"" instead"
+(W deprecated) You have written something like this:
+.Sp
+.Vb 4
+\&    sub doit
+\&    {
+\&        use attrs qw(locked);
+\&    }
+.Ve
+.Sp
+You should use the new declaration syntax instead.
+.Sp
+.Vb 3
+\&    sub doit : locked
+\&    {
+\&        ...
+.Ve
+.Sp
+The \f(CW\*(C`use attrs\*(C'\fR pragma is now obsolete, and is only provided for
+backward-compatibility. See "Subroutine Attributes" in perlsub.
+.IP "Premature end of script headers" 4
+.IX Item "Premature end of script headers"
+See Server error.
+.IP "Repeat count in pack overflows" 4
+.IX Item "Repeat count in pack overflows"
+(F) You can't specify a repeat count so large that it overflows
+your signed integers.  See "pack" in perlfunc.
+.IP "Repeat count in unpack overflows" 4
+.IX Item "Repeat count in unpack overflows"
+(F) You can't specify a repeat count so large that it overflows
+your signed integers.  See "unpack" in perlfunc.
+.IP "\fBrealloc()\fR of freed memory ignored" 4
+.IX Item "realloc() of freed memory ignored"
+(S) An internal routine called \fBrealloc()\fR on something that had already
+been freed.
+.IP "Reference is already weak" 4
+.IX Item "Reference is already weak"
+(W misc) You have attempted to weaken a reference that is already weak.
+Doing so has no effect.
+.IP "setpgrp can't take arguments" 4
+.IX Item "setpgrp can't take arguments"
+(F) Your system has the \fBsetpgrp()\fR from BSD 4.2, which takes no arguments,
+unlike POSIX \fBsetpgid()\fR, which takes a process ID and process group ID.
+.IP "Strange *+?{} on zero-length expression" 4
+.IX Item "Strange *+?{} on zero-length expression"
+(W regexp) You applied a regular expression quantifier in a place where it
+makes no sense, such as on a zero-width assertion.
+Try putting the quantifier inside the assertion instead.  For example,
+the way to match "abc" provided that it is followed by three
+repetitions of "xyz" is \f(CW\*(C`/abc(?=(?:xyz){3})/\*(C'\fR, not \f(CW\*(C`/abc(?=xyz){3}/\*(C'\fR.
+.ie n .IP "switching effective %s is not implemented" 4
+.el .IP "switching effective \f(CW%s\fR is not implemented" 4
+.IX Item "switching effective %s is not implemented"
+(F) While under the \f(CW\*(C`use filetest\*(C'\fR pragma, we cannot switch the
+real and effective uids or gids.
+.IP "This Perl can't reset CRTL environ elements (%s)" 4
+.IX Item "This Perl can't reset CRTL environ elements (%s)"
+.PD 0
+.IP "This Perl can't set CRTL environ elements (%s=%s)" 4
+.IX Item "This Perl can't set CRTL environ elements (%s=%s)"
+.PD
+(W internal) Warnings peculiar to VMS.  You tried to change or delete an element
+of the CRTL's internal environ array, but your copy of Perl wasn't
+built with a CRTL that contained the \fBsetenv()\fR function.  You'll need to
+rebuild Perl with a CRTL that does, or redefine \fIPERL_ENV_TABLES\fR (see
+perlvms) so that the environ array isn't the target of the change to
+\&\f(CW%ENV\fR which produced the warning.
+.ie n .IP "Too late to run %s block" 4
+.el .IP "Too late to run \f(CW%s\fR block" 4
+.IX Item "Too late to run %s block"
+(W void) A CHECK or INIT block is being defined during run time proper,
+when the opportunity to run them has already passed.  Perhaps you are
+loading a file with \f(CW\*(C`require\*(C'\fR or \f(CW\*(C`do\*(C'\fR when you should be using
+\&\f(CW\*(C`use\*(C'\fR instead.  Or perhaps you should put the \f(CW\*(C`require\*(C'\fR or \f(CW\*(C`do\*(C'\fR
+inside a BEGIN block.
+.IP "Unknown \fBopen()\fR mode '%s'" 4
+.IX Item "Unknown open() mode '%s'"
+(F) The second argument of 3\-argument \fBopen()\fR is not among the list
+of valid modes: \f(CW\*(C`<\*(C'\fR, \f(CW\*(C`>\*(C'\fR, \f(CW\*(C`>>\*(C'\fR, \f(CW\*(C`+<\*(C'\fR,
+\&\f(CW\*(C`+>\*(C'\fR, \f(CW\*(C`+>>\*(C'\fR, \f(CW\*(C`\-|\*(C'\fR, \f(CW\*(C`|\-\*(C'\fR.
+.ie n .IP "Unknown process %x sent message to prime_env_iter: %s" 4
+.el .IP "Unknown process \f(CW%x\fR sent message to prime_env_iter: \f(CW%s\fR" 4
+.IX Item "Unknown process %x sent message to prime_env_iter: %s"
+(P) An error peculiar to VMS.  Perl was reading values for \f(CW%ENV\fR before
+iterating over it, and someone else stuck a message in the stream of
+data Perl expected.  Someone's very confused, or perhaps trying to
+subvert Perl's population of \f(CW%ENV\fR for nefarious purposes.
+.IP "Unrecognized escape \e\e%c passed through" 4
+.IX Item "Unrecognized escape %c passed through"
+(W misc) You used a backslash-character combination which is not recognized
+by Perl.  The character was understood literally.
+.IP "Unterminated attribute parameter in attribute list" 4
+.IX Item "Unterminated attribute parameter in attribute list"
+(F) The lexer saw an opening (left) parenthesis character while parsing an
+attribute list, but the matching closing (right) parenthesis
+character was not found.  You may need to add (or remove) a backslash
+character to get your parentheses to balance.  See attributes.
+.IP "Unterminated attribute list" 4
+.IX Item "Unterminated attribute list"
+(F) The lexer found something other than a simple identifier at the start
+of an attribute, and it wasn't a semicolon or the start of a
+block.  Perhaps you terminated the parameter list of the previous attribute
+too soon.  See attributes.
+.IP "Unterminated attribute parameter in subroutine attribute list" 4
+.IX Item "Unterminated attribute parameter in subroutine attribute list"
+(F) The lexer saw an opening (left) parenthesis character while parsing a
+subroutine attribute list, but the matching closing (right) parenthesis
+character was not found.  You may need to add (or remove) a backslash
+character to get your parentheses to balance.
+.IP "Unterminated subroutine attribute list" 4
+.IX Item "Unterminated subroutine attribute list"
+(F) The lexer found something other than a simple identifier at the start
+of a subroutine attribute, and it wasn't a semicolon or the start of a
+block.  Perhaps you terminated the parameter list of the previous attribute
+too soon.
+.IP "Value of CLI symbol ""%s"" too long" 4
+.IX Item "Value of CLI symbol ""%s"" too long"
+(W misc) A warning peculiar to VMS.  Perl tried to read the value of an \f(CW%ENV\fR
+element from a CLI symbol table, and found a resultant string longer
+than 1024 characters.  The return value has been truncated to 1024
+characters.
+.IP "Version number must be a constant number" 4
+.IX Item "Version number must be a constant number"
+(P) The attempt to translate a \f(CW\*(C`use Module n.n LIST\*(C'\fR statement into
+its equivalent \f(CW\*(C`BEGIN\*(C'\fR block found an internal inconsistency with
+the version number.
+.SH "New tests"
+.IX Header "New tests"
+.IP lib/attrs 4
+.IX Item "lib/attrs"
+Compatibility tests for \f(CW\*(C`sub : attrs\*(C'\fR vs the older \f(CW\*(C`use attrs\*(C'\fR.
+.IP lib/env 4
+.IX Item "lib/env"
+Tests for new environment scalar capability (e.g., \f(CW\*(C`use Env qw($BAR);\*(C'\fR).
+.IP lib/env\-array 4
+.IX Item "lib/env-array"
+Tests for new environment array capability (e.g., \f(CW\*(C`use Env qw(@PATH);\*(C'\fR).
+.IP lib/io_const 4
+.IX Item "lib/io_const"
+IO constants (SEEK_*, _IO*).
+.IP lib/io_dir 4
+.IX Item "lib/io_dir"
+Directory-related IO methods (new, read, close, rewind, tied delete).
+.IP lib/io_multihomed 4
+.IX Item "lib/io_multihomed"
+INET sockets with multi-homed hosts.
+.IP lib/io_poll 4
+.IX Item "lib/io_poll"
+IO \fBpoll()\fR.
+.IP lib/io_unix 4
+.IX Item "lib/io_unix"
+UNIX sockets.
+.IP op/attrs 4
+.IX Item "op/attrs"
+Regression tests for \f(CW\*(C`my ($x,@y,%z) : attrs\*(C'\fR and <sub : attrs>.
+.IP op/filetest 4
+.IX Item "op/filetest"
+File test operators.
+.IP op/lex_assign 4
+.IX Item "op/lex_assign"
+Verify operations that access pad objects (lexicals and temporaries).
+.IP op/exists_sub 4
+.IX Item "op/exists_sub"
+Verify \f(CW\*(C`exists &sub\*(C'\fR operations.
+.SH "Incompatible Changes"
+.IX Header "Incompatible Changes"
+.SS "Perl Source Incompatibilities"
+.IX Subsection "Perl Source Incompatibilities"
+Beware that any new warnings that have been added or old ones
+that have been enhanced are \fBnot\fR considered incompatible changes.
+.PP
+Since all new warnings must be explicitly requested via the \f(CW\*(C`\-w\*(C'\fR
+switch or the \f(CW\*(C`warnings\*(C'\fR pragma, it is ultimately the programmer's
+responsibility to ensure that warnings are enabled judiciously.
+.IP "CHECK is a new keyword" 4
+.IX Item "CHECK is a new keyword"
+All subroutine definitions named CHECK are now special.  See
+\&\f(CW\*(C`/"Support for CHECK blocks"\*(C'\fR for more information.
+.IP "Treatment of list slices of undef has changed" 4
+.IX Item "Treatment of list slices of undef has changed"
+There is a potential incompatibility in the behavior of list slices
+that are comprised entirely of undefined values.
+See "Behavior of list slices is more consistent".
+.ie n .IP "Format of $English::PERL_VERSION is different" 4
+.el .IP "Format of \f(CW$English::PERL_VERSION\fR is different" 4
+.IX Item "Format of $English::PERL_VERSION is different"
+The English module now sets \f(CW$PERL_VERSION\fR to $^V (a string value) rather
+than \f(CW$]\fR (a numeric value).  This is a potential incompatibility.
+Send us a report via perlbug if you are affected by this.
+.Sp
+See "Improved Perl version numbering system" for the reasons for
+this change.
+.ie n .IP "Literals of the form 1.2.3 parse differently" 4
+.el .IP "Literals of the form \f(CW1.2.3\fR parse differently" 4
+.IX Item "Literals of the form 1.2.3 parse differently"
+Previously, numeric literals with more than one dot in them were
+interpreted as a floating point number concatenated with one or more
+numbers.  Such "numbers" are now parsed as strings composed of the
+specified ordinals.
+.Sp
+For example, \f(CW\*(C`print 97.98.99\*(C'\fR used to output \f(CW97.9899\fR in earlier
+versions, but now prints \f(CW\*(C`abc\*(C'\fR.
+.Sp
+See "Support for strings represented as a vector of ordinals".
+.IP "Possibly changed pseudo-random number generator" 4
+.IX Item "Possibly changed pseudo-random number generator"
+Perl programs that depend on reproducing a specific set of pseudo-random
+numbers may now produce different output due to improvements made to the
+\&\fBrand()\fR builtin.  You can use \f(CW\*(C`sh Configure \-Drandfunc=rand\*(C'\fR to obtain
+the old behavior.
+.Sp
+See "Better pseudo-random number generator".
+.IP "Hashing function for hash keys has changed" 4
+.IX Item "Hashing function for hash keys has changed"
+Even though Perl hashes are not order preserving, the apparently
+random order encountered when iterating on the contents of a hash
+is actually determined by the hashing algorithm used.  Improvements
+in the algorithm may yield a random order that is \fBdifferent\fR from
+that of previous versions, especially when iterating on hashes.
+.Sp
+See "Better worst-case behavior of hashes" for additional
+information.
+.ie n .IP """undef"" fails on read only values" 4
+.el .IP "\f(CWundef\fR fails on read only values" 4
+.IX Item "undef fails on read only values"
+Using the \f(CW\*(C`undef\*(C'\fR operator on a readonly value (such as \f(CW$1\fR) has
+the same effect as assigning \f(CW\*(C`undef\*(C'\fR to the readonly value\-\-it
+throws an exception.
+.IP "Close-on-exec bit may be set on pipe and socket handles" 4
+.IX Item "Close-on-exec bit may be set on pipe and socket handles"
+Pipe and socket handles are also now subject to the close-on-exec
+behavior determined by the special variable $^F.
+.Sp
+See "More consistent close-on-exec behavior".
+.ie n .IP "Writing ""$$1"" to mean ""${$}1"" is unsupported" 4
+.el .IP "Writing \f(CW""$$1""\fR to mean \f(CW""${$}1""\fR is unsupported" 4
+.IX Item "Writing ""$$1"" to mean ""${$}1"" is unsupported"
+Perl 5.004 deprecated the interpretation of \f(CW$$1\fR and
+similar within interpolated strings to mean \f(CW\*(C`$$ . "1"\*(C'\fR,
+but still allowed it.
+.Sp
+In Perl 5.6.0 and later, \f(CW"$$1"\fR always means \f(CW"${$1}"\fR.
+.ie n .IP "\fBdelete()\fR, \fBeach()\fR, \fBvalues()\fR and ""\e(%h)""" 4
+.el .IP "\fBdelete()\fR, \fBeach()\fR, \fBvalues()\fR and \f(CW\e(%h)\fR" 4
+.IX Item "delete(), each(), values() and )"
+operate on aliases to values, not copies
+.Sp
+\&\fBdelete()\fR, \fBeach()\fR, \fBvalues()\fR and hashes (e.g. \f(CW\*(C`\e(%h)\*(C'\fR)
+in a list context return the actual
+values in the hash, instead of copies (as they used to in earlier
+versions).  Typical idioms for using these constructs copy the
+returned values, but this can make a significant difference when
+creating references to the returned values.  Keys in the hash are still
+returned as copies when iterating on a hash.
+.Sp
+See also "\fBdelete()\fR, \fBeach()\fR, \fBvalues()\fR and hash iteration are faster".
+.IP "vec(EXPR,OFFSET,BITS) enforces powers-of-two BITS" 4
+.IX Item "vec(EXPR,OFFSET,BITS) enforces powers-of-two BITS"
+\&\fBvec()\fR generates a run-time error if the BITS argument is not
+a valid power-of-two integer.
+.IP "Text of some diagnostic output has changed" 4
+.IX Item "Text of some diagnostic output has changed"
+Most references to internal Perl operations in diagnostics
+have been changed to be more descriptive.  This may be an
+issue for programs that may incorrectly rely on the exact
+text of diagnostics for proper functioning.
+.ie n .IP """%@"" has been removed" 4
+.el .IP "\f(CW%@\fR has been removed" 4
+.IX Item "%@ has been removed"
+The undocumented special variable \f(CW\*(C`%@\*(C'\fR that used to accumulate
+"background" errors (such as those that happen in \fBDESTROY()\fR)
+has been removed, because it could potentially result in memory
+leaks.
+.IP "Parenthesized \fBnot()\fR behaves like a list operator" 4
+.IX Item "Parenthesized not() behaves like a list operator"
+The \f(CW\*(C`not\*(C'\fR operator now falls under the "if it looks like a function,
+it behaves like a function" rule.
+.Sp
+As a result, the parenthesized form can be used with \f(CW\*(C`grep\*(C'\fR and \f(CW\*(C`map\*(C'\fR.
+The following construct used to be a syntax error before, but it works
+as expected now:
+.Sp
+.Vb 1
+\&    grep not($_), @things;
+.Ve
+.Sp
+On the other hand, using \f(CW\*(C`not\*(C'\fR with a literal list slice may not
+work.  The following previously allowed construct:
+.Sp
+.Vb 1
+\&    print not (1,2,3)[0];
+.Ve
+.Sp
+needs to be written with additional parentheses now:
+.Sp
+.Vb 1
+\&    print not((1,2,3)[0]);
+.Ve
+.Sp
+The behavior remains unaffected when \f(CW\*(C`not\*(C'\fR is not followed by parentheses.
+.ie n .IP "Semantics of bareword prototype ""(*)"" have changed" 4
+.el .IP "Semantics of bareword prototype \f(CW(*)\fR have changed" 4
+.IX Item "Semantics of bareword prototype (*) have changed"
+The semantics of the bareword prototype \f(CW\*(C`*\*(C'\fR have changed.  Perl 5.005
+always coerced simple scalar arguments to a typeglob, which wasn't useful
+in situations where the subroutine must distinguish between a simple
+scalar and a typeglob.  The new behavior is to not coerce bareword
+arguments to a typeglob.  The value will always be visible as either
+a simple scalar or as a reference to a typeglob.
+.Sp
+See "More functional bareword prototype (*)".
+.IP "Semantics of bit operators may have changed on 64\-bit platforms" 4
+.IX Item "Semantics of bit operators may have changed on 64-bit platforms"
+If your platform is either natively 64\-bit or if Perl has been
+configured to used 64\-bit integers, i.e., \f(CW$Config\fR{ivsize} is 8, 
+there may be a potential incompatibility in the behavior of bitwise
+numeric operators (& | ^ ~ << >>).  These operators used to strictly
+operate on the lower 32 bits of integers in previous versions, but now
+operate over the entire native integral width.  In particular, note
+that unary \f(CW\*(C`~\*(C'\fR will produce different results on platforms that have
+different \f(CW$Config\fR{ivsize}.  For portability, be sure to mask off
+the excess bits in the result of unary \f(CW\*(C`~\*(C'\fR, e.g., \f(CW\*(C`~$x & 0xffffffff\*(C'\fR.
+.Sp
+See "Bit operators support full native integer width".
+.IP "More builtins taint their results" 4
+.IX Item "More builtins taint their results"
+As described in "Improved security features", there may be more
+sources of taint in a Perl program.
+.Sp
+To avoid these new tainting behaviors, you can build Perl with the
+Configure option \f(CW\*(C`\-Accflags=\-DINCOMPLETE_TAINTS\*(C'\fR.  Beware that the
+ensuing perl binary may be insecure.
+.SS "C Source Incompatibilities"
+.IX Subsection "C Source Incompatibilities"
+.ie n .IP """PERL_POLLUTE""" 4
+.el .IP \f(CWPERL_POLLUTE\fR 4
+.IX Item "PERL_POLLUTE"
+Release 5.005 grandfathered old global symbol names by providing preprocessor
+macros for extension source compatibility.  As of release 5.6.0, these
+preprocessor definitions are not available by default.  You need to explicitly
+compile perl with \f(CW\*(C`\-DPERL_POLLUTE\*(C'\fR to get these definitions.  For
+extensions still using the old symbols, this option can be
+specified via MakeMaker:
+.Sp
+.Vb 1
+\&    perl Makefile.PL POLLUTE=1
+.Ve
+.ie n .IP """PERL_IMPLICIT_CONTEXT""" 4
+.el .IP \f(CWPERL_IMPLICIT_CONTEXT\fR 4
+.IX Item "PERL_IMPLICIT_CONTEXT"
+This new build option provides a set of macros for all API functions
+such that an implicit interpreter/thread context argument is passed to
+every API function.  As a result of this, something like \f(CW\*(C`sv_setsv(foo,bar)\*(C'\fR
+amounts to a macro invocation that actually translates to something like
+\&\f(CW\*(C`Perl_sv_setsv(my_perl,foo,bar)\*(C'\fR.  While this is generally expected
+to not have any significant source compatibility issues, the difference
+between a macro and a real function call will need to be considered.
+.Sp
+This means that there \fBis\fR a source compatibility issue as a result of
+this if your extensions attempt to use pointers to any of the Perl API
+functions.
+.Sp
+Note that the above issue is not relevant to the default build of
+Perl, whose interfaces continue to match those of prior versions
+(but subject to the other options described here).
+.Sp
+See "Background and PERL_IMPLICIT_CONTEXT" in perlguts for detailed information on the
+ramifications of building Perl with this option.
+.Sp
+.Vb 3
+\&    NOTE: PERL_IMPLICIT_CONTEXT is automatically enabled whenever Perl is built
+\&    with one of \-Dusethreads, \-Dusemultiplicity, or both.  It is not
+\&    intended to be enabled by users at this time.
+.Ve
+.ie n .IP """PERL_POLLUTE_MALLOC""" 4
+.el .IP \f(CWPERL_POLLUTE_MALLOC\fR 4
+.IX Item "PERL_POLLUTE_MALLOC"
+Enabling Perl's malloc in release 5.005 and earlier caused the namespace of
+the system's malloc family of functions to be usurped by the Perl versions,
+since by default they used the same names.  Besides causing problems on
+platforms that do not allow these functions to be cleanly replaced, this
+also meant that the system versions could not be called in programs that
+used Perl's malloc.  Previous versions of Perl have allowed this behaviour
+to be suppressed with the HIDEMYMALLOC and EMBEDMYMALLOC preprocessor
+definitions.
+.Sp
+As of release 5.6.0, Perl's malloc family of functions have default names
+distinct from the system versions.  You need to explicitly compile perl with
+\&\f(CW\*(C`\-DPERL_POLLUTE_MALLOC\*(C'\fR to get the older behaviour.  HIDEMYMALLOC
+and EMBEDMYMALLOC have no effect, since the behaviour they enabled is now
+the default.
+.Sp
+Note that these functions do \fBnot\fR constitute Perl's memory allocation API.
+See "Memory Allocation" in perlguts for further information about that.
+.SS "Compatible C Source API Changes"
+.IX Subsection "Compatible C Source API Changes"
+.ie n .IP """PATCHLEVEL"" is now ""PERL_VERSION""" 4
+.el .IP "\f(CWPATCHLEVEL\fR is now \f(CWPERL_VERSION\fR" 4
+.IX Item "PATCHLEVEL is now PERL_VERSION"
+The cpp macros \f(CW\*(C`PERL_REVISION\*(C'\fR, \f(CW\*(C`PERL_VERSION\*(C'\fR, and \f(CW\*(C`PERL_SUBVERSION\*(C'\fR
+are now available by default from perl.h, and reflect the base revision,
+patchlevel, and subversion respectively.  \f(CW\*(C`PERL_REVISION\*(C'\fR had no
+prior equivalent, while \f(CW\*(C`PERL_VERSION\*(C'\fR and \f(CW\*(C`PERL_SUBVERSION\*(C'\fR were
+previously available as \f(CW\*(C`PATCHLEVEL\*(C'\fR and \f(CW\*(C`SUBVERSION\*(C'\fR.
+.Sp
+The new names cause less pollution of the \fBcpp\fR namespace and reflect what
+the numbers have come to stand for in common practice.  For compatibility,
+the old names are still supported when \fIpatchlevel.h\fR is explicitly
+included (as required before), so there is no source incompatibility
+from the change.
+.SS "Binary Incompatibilities"
+.IX Subsection "Binary Incompatibilities"
+In general, the default build of this release is expected to be binary
+compatible for extensions built with the 5.005 release or its maintenance
+versions.  However, specific platforms may have broken binary compatibility
+due to changes in the defaults used in hints files.  Therefore, please be
+sure to always check the platform-specific README files for any notes to
+the contrary.
+.PP
+The usethreads or usemultiplicity builds are \fBnot\fR binary compatible
+with the corresponding builds in 5.005.
+.PP
+On platforms that require an explicit list of exports (AIX, OS/2 and Windows,
+among others), purely internal symbols such as parser functions and the
+run time opcodes are not exported by default.  Perl 5.005 used to export
+all functions irrespective of whether they were considered part of the
+public API or not.
+.PP
+For the full list of public API functions, see perlapi.
+.SH "Known Problems"
+.IX Header "Known Problems"
+.SS "Thread test failures"
+.IX Subsection "Thread test failures"
+The subtests 19 and 20 of lib/thr5005.t test are known to fail due to
+fundamental problems in the 5.005 threading implementation.  These are
+not new failures\-\-Perl 5.005_0x has the same bugs, but didn't have these
+tests.
+.SS "EBCDIC platforms not supported"
+.IX Subsection "EBCDIC platforms not supported"
+In earlier releases of Perl, EBCDIC environments like OS390 (also
+known as Open Edition MVS) and VM-ESA were supported.  Due to changes
+required by the UTF\-8 (Unicode) support, the EBCDIC platforms are not
+supported in Perl 5.6.0.
+.SS "In 64\-bit HP-UX the lib/io_multihomed test may hang"
+.IX Subsection "In 64-bit HP-UX the lib/io_multihomed test may hang"
+The lib/io_multihomed test may hang in HP-UX if Perl has been
+configured to be 64\-bit.  Because other 64\-bit platforms do not
+hang in this test, HP-UX is suspect.  All other tests pass
+in 64\-bit HP-UX.  The test attempts to create and connect to
+"multihomed" sockets (sockets which have multiple IP addresses).
+.SS "NEXTSTEP 3.3 POSIX test failure"
+.IX Subsection "NEXTSTEP 3.3 POSIX test failure"
+In NEXTSTEP 3.3p2 the implementation of the \fBstrftime\fR\|(3) in the
+operating system libraries is buggy: the \f(CW%j\fR format numbers the days of
+a month starting from zero, which, while being logical to programmers,
+will cause the subtests 19 to 27 of the lib/posix test may fail.
+.SS "Tru64 (aka Digital UNIX, aka DEC OSF/1) lib/sdbm test failure with gcc"
+.IX Subsection "Tru64 (aka Digital UNIX, aka DEC OSF/1) lib/sdbm test failure with gcc"
+If compiled with gcc 2.95 the lib/sdbm test will fail (dump core).
+The cure is to use the vendor cc, it comes with the operating system
+and produces good code.
+.SS "UNICOS/mk CC failures during Configure run"
+.IX Subsection "UNICOS/mk CC failures during Configure run"
+In UNICOS/mk the following errors may appear during the Configure run:
+.PP
+.Vb 6
+\&        Guessing which symbols your C compiler and preprocessor define...
+\&        CC\-20 cc: ERROR File = try.c, Line = 3
+\&        ...
+\&          bad switch yylook 79bad switch yylook 79bad switch yylook 79bad switch yylook 79#ifdef A29K
+\&        ...
+\&        4 errors detected in the compilation of "try.c".
+.Ve
+.PP
+The culprit is the broken awk of UNICOS/mk.  The effect is fortunately
+rather mild: Perl itself is not adversely affected by the error, only
+the h2ph utility coming with Perl, and that is rather rarely needed
+these days.
+.SS "Arrow operator and arrays"
+.IX Subsection "Arrow operator and arrays"
+When the left argument to the arrow operator \f(CW\*(C`\->\*(C'\fR is an array, or
+the \f(CW\*(C`scalar\*(C'\fR operator operating on an array, the result of the
+operation must be considered erroneous. For example:
+.PP
+.Vb 2
+\&    @x\->[2]
+\&    scalar(@x)\->[2]
+.Ve
+.PP
+These expressions will get run-time errors in some future release of
+Perl.
+.SS "Experimental features"
+.IX Subsection "Experimental features"
+As discussed above, many features are still experimental.  Interfaces and
+implementation of these features are subject to change, and in extreme cases,
+even subject to removal in some future release of Perl.  These features
+include the following:
+.IP Threads 4
+.IX Item "Threads"
+.PD 0
+.IP Unicode 4
+.IX Item "Unicode"
+.IP "64\-bit support" 4
+.IX Item "64-bit support"
+.IP "Lvalue subroutines" 4
+.IX Item "Lvalue subroutines"
+.IP "Weak references" 4
+.IX Item "Weak references"
+.IP "The pseudo-hash data type" 4
+.IX Item "The pseudo-hash data type"
+.IP "The Compiler suite" 4
+.IX Item "The Compiler suite"
+.IP "Internal implementation of file globbing" 4
+.IX Item "Internal implementation of file globbing"
+.IP "The DB module" 4
+.IX Item "The DB module"
+.IP "The regular expression code constructs:" 4
+.IX Item "The regular expression code constructs:"
+.PD
+\&\f(CW\*(C`(?{ code })\*(C'\fR and \f(CW\*(C`(??{ code })\*(C'\fR
+.SH "Obsolete Diagnostics"
+.IX Header "Obsolete Diagnostics"
+.IP "Character class syntax [: :] is reserved for future extensions" 4
+.IX Item "Character class syntax [: :] is reserved for future extensions"
+(W) Within regular expression character classes ([]) the syntax beginning
+with "[:" and ending with ":]" is reserved for future extensions.
+If you need to represent those character sequences inside a regular
+expression character class, just quote the square brackets with the
+backslash: "\e[:" and ":\e]".
+.IP "Ill-formed logical name |%s| in prime_env_iter" 4
+.IX Item "Ill-formed logical name |%s| in prime_env_iter"
+(W) A warning peculiar to VMS.  A logical name was encountered when preparing
+to iterate over \f(CW%ENV\fR which violates the syntactic rules governing logical
+names.  Because it cannot be translated normally, it is skipped, and will not
+appear in \f(CW%ENV\fR.  This may be a benign occurrence, as some software packages
+might directly modify logical name tables and introduce nonstandard names,
+or it may indicate that a logical name table has been corrupted.
+.IP "In string, @%s now must be written as \e@%s" 4
+.IX Item "In string, @%s now must be written as @%s"
+The description of this error used to say:
+.Sp
+.Vb 2
+\&        (Someday it will simply assume that an unbackslashed @
+\&         interpolates an array.)
+.Ve
+.Sp
+That day has come, and this fatal error has been removed.  It has been
+replaced by a non-fatal warning instead.
+See "Arrays now always interpolate into double-quoted strings" for
+details.
+.ie n .IP "Probable precedence problem on %s" 4
+.el .IP "Probable precedence problem on \f(CW%s\fR" 4
+.IX Item "Probable precedence problem on %s"
+(W) The compiler found a bareword where it expected a conditional,
+which often indicates that an || or && was parsed as part of the
+last argument of the previous construct, for example:
+.Sp
+.Vb 1
+\&    open FOO || die;
+.Ve
+.IP "regexp too big" 4
+.IX Item "regexp too big"
+(F) The current implementation of regular expressions uses shorts as
+address offsets within a string.  Unfortunately this means that if
+the regular expression compiles to longer than 32767, it'll blow up.
+Usually when you want a regular expression this big, there is a better
+way to do it with multiple statements.  See perlre.
+.IP "Use of ""$$<digit>"" to mean ""${$}<digit>"" is deprecated" 4
+.IX Item "Use of ""$$<digit>"" to mean ""${$}<digit>"" is deprecated"
+(D) Perl versions before 5.004 misinterpreted any type marker followed
+by "$" and a digit.  For example, "$$0" was incorrectly taken to mean
+"${$}0" instead of "${$0}".  This bug is (mostly) fixed in Perl 5.004.
+.Sp
+However, the developers of Perl 5.004 could not fix this bug completely,
+because at least two widely-used modules depend on the old meaning of
+"$$0" in a string.  So Perl 5.004 still interprets "$$<digit>" in the
+old (broken) way inside strings; but it generates this message as a
+warning.  And in Perl 5.005, this special treatment will cease.
+.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.
+There may also be information at http://www.perl.com/perl/ , the Perl
+Home Page.
+.PP
+If you believe you have an unreported bug, please run the \fBperlbug\fR
+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.
+.SH "SEE ALSO"
+.IX Header "SEE ALSO"
+The \fIChanges\fR file for 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.
+.SH HISTORY
+.IX Header "HISTORY"
+Written by Gurusamy Sarathy <\fIgsar@activestate.com\fR>, with many
+contributions from The Perl Porters.
+.PP
+Send omissions or corrections to <\fIperlbug@perl.org\fR>.