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Attribute	[ DIR ]	drwxr-xr-x	2025-07-15 16:48
B	[ DIR ]	drwxr-xr-x	2025-07-15 16:48
CPAN	[ DIR ]	drwxr-xr-x	2025-07-15 16:57
Class	[ DIR ]	drwxr-xr-x	2025-07-15 16:48
Compress	[ DIR ]	drwxr-xr-x	2025-07-15 16:48
Config	[ DIR ]	drwxr-xr-x	2025-07-15 16:48
DBM_Filter	[ DIR ]	drwxr-xr-x	2025-07-15 16:48
Devel	[ DIR ]	drwxr-xr-x	2025-07-15 16:48
ExtUtils	[ DIR ]	drwxr-xr-x	2025-07-15 16:49
File	[ DIR ]	drwxr-xr-x	2025-07-15 16:48
Getopt	[ DIR ]	drwxr-xr-x	2025-07-15 16:48
I18N	[ DIR ]	drwxr-xr-x	2025-07-15 16:48
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Locale	[ DIR ]	drwxr-xr-x	2025-07-15 16:48
Math	[ DIR ]	drwxr-xr-x	2025-07-15 16:48
Memoize	[ DIR ]	drwxr-xr-x	2025-07-15 16:48
Module	[ DIR ]	drwxr-xr-x	2025-07-15 16:48
Net	[ DIR ]	drwxr-xr-x	2025-07-15 16:48
Pod	[ DIR ]	drwxr-xr-x	2025-07-15 16:48
Search	[ DIR ]	drwxr-xr-x	2025-07-15 16:48
Term	[ DIR ]	drwxr-xr-x	2025-07-15 16:48
Text	[ DIR ]	drwxr-xr-x	2025-07-15 16:48
Thread	[ DIR ]	drwxr-xr-x	2025-07-15 16:48
Tie	[ DIR ]	drwxr-xr-x	2025-07-15 16:49
Time	[ DIR ]	drwxr-xr-x	2025-07-15 16:49
URI	[ DIR ]	drwxr-xr-x	2025-07-15 16:48
Unicode	[ DIR ]	drwxr-xr-x	2025-07-15 16:48
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encoding	[ DIR ]	drwxr-xr-x	2025-07-15 16:49
overload	[ DIR ]	drwxr-xr-x	2025-07-15 16:48
pod	[ DIR ]	drwxr-xr-x	2025-07-15 16:48
unicore	[ DIR ]	drwxr-xr-x	2025-07-15 16:48
vendor_perl	[ DIR ]	drwxr-xr-x	2025-07-16 12:36
warnings	[ DIR ]	drwxr-xr-x	2025-07-15 16:48
AnyDBM_File.pm	2.56 KB	-rw-r--r--	2024-04-03 14:35
AutoLoader.pm	15.43 KB	-rw-r--r--	2024-04-03 14:39
AutoSplit.pm	19.18 KB	-rw-r--r--	2024-04-03 14:39
Benchmark.pm	30.3 KB	-rw-r--r--	2024-04-03 14:39
CORE.pod	3.11 KB	-rw-r--r--	2024-04-03 14:35
DB.pm	18.48 KB	-rw-r--r--	2024-04-03 14:39
DBM_Filter.pm	14.05 KB	-rw-r--r--	2024-04-03 14:39
DirHandle.pm	2.04 KB	-rw-r--r--	2024-04-03 14:39
Dumpvalue.pm	17.25 KB	-rw-r--r--	2024-04-03 14:39
English.pm	4.65 KB	-rw-r--r--	2024-04-03 14:39
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FileHandle.pm	6.63 KB	-rw-r--r--	2024-04-03 14:39
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PerlIO.pm	14.1 KB	-rw-r--r--	2024-04-03 14:35
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SelectSaver.pm	1.05 KB	-rw-r--r--	2024-04-03 14:39
SelfLoader.pm	17.27 KB	-rw-r--r--	2024-04-03 14:39
Symbol.pm	4.69 KB	-rw-r--r--	2024-04-03 14:39
Test.pm	29.34 KB	-rw-r--r--	2024-04-03 14:39
Thread.pm	8.09 KB	-rw-r--r--	2024-04-03 14:39
UNIVERSAL.pm	6.44 KB	-rw-r--r--	2024-04-03 14:35
URI.pm	34.13 KB	-rw-r--r--	2021-03-03 15:16
XSLoader.pm	10.99 KB	-rw-r--r--	2024-04-03 14:35
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autouse.pm	4.14 KB	-rw-r--r--	2024-04-03 14:39
base.pm	10.7 KB	-rw-r--r--	2024-04-03 14:39
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bytes.pm	3.65 KB	-rw-r--r--	2024-04-03 14:35
bytes_heavy.pl	758 B	-rw-r--r--	2024-04-03 14:35
charnames.pm	20.44 KB	-rw-r--r--	2024-04-03 14:35
deprecate.pm	4.5 KB	-rw-r--r--	2024-04-03 14:39
diagnostics.pm	18.85 KB	-rw-r--r--	2024-04-03 14:39
dumpvar.pl	15.19 KB	-rw-r--r--	2024-04-03 14:39
feature.pm	18.56 KB	-rw-r--r--	2024-04-03 14:35
fields.pm	9.25 KB	-rw-r--r--	2024-04-03 14:39
filetest.pm	3.91 KB	-rw-r--r--	2024-04-03 14:39
if.pm	3.53 KB	-rw-r--r--	2024-04-03 14:39
integer.pm	3.18 KB	-rw-r--r--	2024-04-03 14:35
less.pm	3.13 KB	-rw-r--r--	2024-04-03 14:39
locale.pm	4.74 KB	-rw-r--r--	2024-04-03 14:39
meta_notation.pm	2.07 KB	-rw-r--r--	2024-04-03 14:39
open.pm	8.31 KB	-rw-r--r--	2024-04-03 14:39
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overloading.pm	1.77 KB	-rw-r--r--	2024-04-03 14:39
perl5db.pl	309.66 KB	-rw-r--r--	2024-04-03 14:39
sigtrap.pm	8.53 KB	-rw-r--r--	2024-04-03 14:39
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strict.pm	4.63 KB	-rw-r--r--	2024-04-03 14:35
subs.pm	901 B	-rw-r--r--	2024-04-03 14:39
utf8.pm	10.18 KB	-rw-r--r--	2024-04-03 14:35
vars.pm	2.4 KB	-rw-r--r--	2024-04-03 14:39
vmsish.pm	4.21 KB	-rw-r--r--	2024-04-03 14:39
warnings.pm	49.35 KB	-rw-r--r--	2024-04-03 14:35

Rename

package if;

$VERSION = '0.0608';

sub work {
  my $method = shift() ? 'import' : 'unimport';
  unless (@_ >= 2) {
    my $type = ($method eq 'import') ? 'use' : 'no';
    die "Too few arguments to '$type if' (some code returning an empty list in list context?)"
  }
  return unless shift;		# CONDITION

my $p = $_[0];		# PACKAGE
  (my $file = "$p.pm") =~ s!::!/!g;
  require $file;		# Works even if $_[0] is a keyword (like open)
  my $m = $p->can($method);
  goto &$m if $m;
}

sub import   { shift; unshift @_, 1; goto &work }
sub unimport { shift; unshift @_, 0; goto &work }

1;
__END__

=head1 NAME

if - C<use> a Perl module if a condition holds

=head1 SYNOPSIS

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

=head1 DESCRIPTION

=head2 C<use if>

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

use if CONDITION, "MODULE", ARGUMENTS;

... will load C<MODULE> only if C<CONDITION> evaluates to true; it has no
effect if C<CONDITION> evaluates to false.  (The module name, assuming it
contains at least one C<::>, must be quoted when C<'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 F<Unicode::UCD> module's F<charinfo> function will use two functions from F<Unicode::Normalize> only if a certain condition is met:

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

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

use MODULE ();

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

BEGIN { require MODULE if CONDITION }

=head2 C<no if>

The C<no if> construct is mainly used to deactivate categories of warnings
when those categories would produce superfluous output under specified
versions of F<perl>.

For example, the C<redundant> category of warnings was introduced in
Perl-5.22.  This warning flags certain instances of superfluous arguments to
C<printf> and C<sprintf>.  But if your code was running warnings-free on
earlier versions of F<perl> and you don't care about C<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 C<no if> construct assumes that a module or pragma has correctly
implemented an C<unimport()> method -- but most modules and pragmata have not.
That explains why the C<no if> construct is of limited applicability.

=head1 BUGS

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

=head1 SEE ALSO

L<Module::Requires> can be used to conditionally load one or modules,
with constraints based on the version of the module.
Unlike C<if> though, L<Module::Requires> is not a core module.

L<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 L<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.

=head1 AUTHOR

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

=head1 COPYRIGHT AND LICENCE

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

=cut