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Updated: Thursday, June 13, 2019
 
 

if (3)

Name

if - "use" a Perl module if a condition holds (also can "no" a module)

Synopsis

use if CONDITION, MODULE => ARGUMENTS;
no if CONDITION, MODULE => ARGUMENTS;

Description

Perl Programmers Reference Guide                                         if(3)



NAME
       if - "use" a Perl module if a condition holds (also can "no" a module)

SYNOPSIS
         use if CONDITION, MODULE => ARGUMENTS;
         no if CONDITION, MODULE => ARGUMENTS;

DESCRIPTION
       The "if" module is used to conditionally load or unload another module.
       The construct

         use if CONDITION, MODULE => ARGUMENTS;

       will load MODULE only if CONDITION evaluates to true.  The above
       statement has no effect unless "CONDITION" is true.  If the CONDITION
       does evaluate to true, then the above line has the same effect as:

         use MODULE ARGUMENTS;

       The use of "=>" above provides necessary quoting of "MODULE".  If you
       don't use the fat comma (eg you don't have any ARGUMENTS), then you'll
       need to quote the MODULE.

   EXAMPLES
       The following line is taken from the testsuite for File::Map:

         use if $^O ne 'MSWin32', POSIX => qw/setlocale LC_ALL/;

       If run on any operating system other than Windows, this will import the
       functions "setlocale" and "LC_ALL" from POSIX.  On Windows it does
       nothing.

       The following is used to deprecate core modules beyond a certain
       version of Perl:

         use if $] > 5.016, 'deprecate';

       This line is taken from Text::Soundex 3.04, and marks it as deprecated
       beyond Perl 5.16.  If you "use Text::Soundex" in Perl 5.18, for
       example, and you have used warnings, then you'll get a warning message
       (the deprecate module looks to see whether the calling module was
       "use"'d from a core library directory, and if so, generates a warning),
       unless you've installed a more recent version of Text::Soundex from
       CPAN.

       You can also specify to NOT use something:

        no if $] ge 5.021_006, warnings => "locale";

       This warning category was added in the specified Perl version (a
       development release).  Without the 'if', trying to use it in an earlier
       release would generate an unknown warning category error.

BUGS
       The current implementation does not allow specification of the required
       version of the module.


ATTRIBUTES
       See attributes(7) for descriptions of the following attributes:


       +---------------+-----------------------+
       |ATTRIBUTE TYPE |   ATTRIBUTE VALUE     |
       +---------------+-----------------------+
       |Availability   | runtime/perl-526      |
       +---------------+-----------------------+
       |Stability      | Pass-through volatile |
       +---------------+-----------------------+
SEE ALSO
       Module::Requires can be used to conditionally load one or modules, with
       constraints based on the version of the module.  Unlike "if" though,
       Module::Requires is not a core module.

       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.

       provide can be used to select one of several possible modules to load,
       based on what version of Perl is running.

AUTHOR
       Ilya Zakharevich <mailto:ilyaz@cpan.org>.

COPYRIGHT AND LICENCE
       This software is copyright (c) 2002 by Ilya Zakharevich.

       This is free software; you can redistribute it and/or modify it under
       the same terms as the Perl 5 programming language system itself.



NOTES
       This software was built from source available at
       https://github.com/oracle/solaris-userland.  The original community
       source was downloaded from
       http://www.cpan.org/src/5.0/perl-5.26.3.tar.bz2

       Further information about this software can be found on the open source
       community website at http://www.perl.org/.



perl v5.26.3                      2018-03-01                             if(3)