if(3pm)

💖 NAME 💖

okay bestie, welcome to the if(3pm) page from the Perl Programmers Reference Guide 💅✨

if — "use" a Perl module if a condition holds 🫶

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✨ SYNOPSIS ✨

use if CONDITION, "MODULE", ARGUMENTS;
no  if CONDITION, "MODULE", ARGUMENTS;

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💖 DESCRIPTION 💖

🦋 "use if" 🦋

The if module is used to conditionally load another module. The construct:

use if CONDITION, "MODULE", ARGUMENTS;

... will load MODULE only if CONDITION evaluates to true; it has no effect if CONDITION evaluates to false. (The module name, assuming it contains at least one ::, must be quoted when use strict "subs"; is in effect.) If the CONDITION does evaluate to true, then the above line has the same effect as:

use MODULE ARGUMENTS;

For example, the Unicode::UCD module's charinfo function will use two functions from Unicode::Normalize only if a certain condition is met:

use if defined &DynaLoader::boot_DynaLoader,
    "Unicode::Normalize" => qw(getCombinClass NFD);

Suppose you wanted ARGUMENTS to be an empty list, i.e., to have the effect of:

use MODULE ();

You can't do this with the if pragma; however, you can achieve exactly this effect, at compile time, with:

BEGIN { require MODULE if CONDITION }

🦋 "no if" 🦋

The no if construct is mainly used to deactivate categories of warnings when those categories would produce superfluous output under specified versions of perl. iykyk 😌

For example, the redundant category of warnings was introduced in Perl-5.22. This warning flags certain instances of superfluous arguments to printf and sprintf. But if your code was running warnings-free on earlier versions of perl and you don't care about redundant warnings in more recent versions, you can call:

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}};

The no if construct assumes that a module or pragma has correctly implemented an unimport() method -- but most modules and pragmata have not. That explains why the no if construct is of limited applicability. fr fr 🫠

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💀 BUGS 💀

The current implementation does not allow specification of the required version of the module. not me discovering this limitation 😭

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🌈 SEE ALSO 🌈

• Module::Requires can be used to conditionally load one or more 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.
• 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.

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👑 AUTHOR 👑

Ilya Zakharevich <mailto:ilyaz@cpan.org>. iconic behavior honestly 💖

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🎀 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.

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okay that's the whole if(3pm) page — source/version perl v5.42.3, dated 2026-11-03 — bye bestie, go conditionally load something slay 💅✨