if

NAME
SYNOPSIS
DESCRIPTION

EXAMPLES

BUGS
SEE ALSO
AUTHOR

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.