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Diffstat (limited to 'upstream/debian-unstable/man3/if.3perl')
| -rw-r--r-- | upstream/debian-unstable/man3/if.3perl | 159 |
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diff --git a/upstream/debian-unstable/man3/if.3perl b/upstream/debian-unstable/man3/if.3perl new file mode 100644 index 00000000..afe3a8db --- /dev/null +++ b/upstream/debian-unstable/man3/if.3perl @@ -0,0 +1,159 @@ +.\" -*- 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 "if 3perl" +.TH if 3perl 2024-01-12 "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 +if \- "use" a Perl module if a condition holds +.SH SYNOPSIS +.IX Header "SYNOPSIS" +.Vb 2 +\& use if CONDITION, "MODULE", ARGUMENTS; +\& no if CONDITION, "MODULE", ARGUMENTS; +.Ve +.SH DESCRIPTION +.IX Header "DESCRIPTION" +.ie n .SS """use if""" +.el .SS "\f(CWuse if\fP" +.IX Subsection "use if" +The \f(CW\*(C`if\*(C'\fR module is used to conditionally load another module. The construct: +.PP +.Vb 1 +\& use if CONDITION, "MODULE", ARGUMENTS; +.Ve +.PP +\&... will load \f(CW\*(C`MODULE\*(C'\fR only if \f(CW\*(C`CONDITION\*(C'\fR evaluates to true; it has no +effect if \f(CW\*(C`CONDITION\*(C'\fR evaluates to false. (The module name, assuming it +contains at least one \f(CW\*(C`::\*(C'\fR, must be quoted when \f(CW\*(Aquse strict "subs";\*(Aq\fR is in +effect.) If the CONDITION does evaluate to true, then the above line has the +same effect as: +.PP +.Vb 1 +\& use MODULE ARGUMENTS; +.Ve +.PP +For example, the \fIUnicode::UCD\fR module's \fIcharinfo\fR function will use two functions from \fIUnicode::Normalize\fR only if a certain condition is met: +.PP +.Vb 2 +\& use if defined &DynaLoader::boot_DynaLoader, +\& "Unicode::Normalize" => qw(getCombinClass NFD); +.Ve +.PP +Suppose you wanted \f(CW\*(C`ARGUMENTS\*(C'\fR to be an empty list, \fIi.e.\fR, to have the +effect of: +.PP +.Vb 1 +\& use MODULE (); +.Ve +.PP +You can't do this with the \f(CW\*(C`if\*(C'\fR pragma; however, you can achieve +exactly this effect, at compile time, with: +.PP +.Vb 1 +\& BEGIN { require MODULE if CONDITION } +.Ve +.ie n .SS """no if""" +.el .SS "\f(CWno if\fP" +.IX Subsection "no if" +The \f(CW\*(C`no if\*(C'\fR construct is mainly used to deactivate categories of warnings +when those categories would produce superfluous output under specified +versions of \fIperl\fR. +.PP +For example, the \f(CW\*(C`redundant\*(C'\fR category of warnings was introduced in +Perl\-5.22. This warning flags certain instances of superfluous arguments to +\&\f(CW\*(C`printf\*(C'\fR and \f(CW\*(C`sprintf\*(C'\fR. But if your code was running warnings-free on +earlier versions of \fIperl\fR and you don't care about \f(CW\*(C`redundant\*(C'\fR warnings in +more recent versions, you can call: +.PP +.Vb 2 +\& use warnings; +\& no if $] >= 5.022, q|warnings|, qw(redundant); +\& +\& my $test = { fmt => "%s", args => [ qw( x y ) ] }; +\& my $result = sprintf $test\->{fmt}, @{$test\->{args}}; +.Ve +.PP +The \f(CW\*(C`no if\*(C'\fR construct assumes that a module or pragma has correctly +implemented an \f(CWunimport()\fR method \-\- but most modules and pragmata have not. +That explains why the \f(CW\*(C`no if\*(C'\fR construct is of limited applicability. +.SH BUGS +.IX Header "BUGS" +The current implementation does not allow specification of the required +version of the module. +.SH "SEE ALSO" +.IX Header "SEE ALSO" +Module::Requires can be used to conditionally load one or more modules, +with constraints based on the version of the module. +Unlike \f(CW\*(C`if\*(C'\fR though, Module::Requires is not a core module. +.PP +Module::Load::Conditional provides a number of functions you can use to +query what modules are available, and then load one or more of them at runtime. +.PP +The provide module from CPAN can be used to select one of several possible +modules to load based on the version of Perl that is running. +.SH AUTHOR +.IX Header "AUTHOR" +Ilya Zakharevich <mailto:ilyaz@cpan.org>. +.SH "COPYRIGHT AND LICENCE" +.IX Header "COPYRIGHT AND LICENCE" +This software is copyright (c) 2002 by Ilya Zakharevich. +.PP +This is free software; you can redistribute it and/or modify it under +the same terms as the Perl 5 programming language system itself. |