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if(3pm)                Perl Programmers Reference Guide                if(3pm)




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.


SEE ALSO

       Module::Requires(3) 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(3) 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.



perl v5.24.0                      2016-03-01                           if(3pm)

perl 5.24 - Generated Sun Nov 13 15:41:02 CST 2016
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