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            <h1>if</h1>


  <!--    -->
<ul><li><a href="#NAME">NAME</a><li><a href="#SYNOPSIS">SYNOPSIS</a><li><a href="#DESCRIPTION">DESCRIPTION</a><ul><li><a href="#EXAMPLES">EXAMPLES</a></ul><li><a href="#BUGS">BUGS</a><li><a href="#SEE-ALSO">SEE ALSO</a><li><a href="#AUTHOR">AUTHOR</a><li><a href="#COPYRIGHT-AND-LICENCE">COPYRIGHT AND LICENCE</a></ul><a name="NAME"></a><h1>NAME</h1>
<p>if - <code class="inline"><a class="l_k" href="functions/use.html">use</a></code> a Perl module if a condition holds (also can <code class="inline"><a class="l_k" href="functions/no.html">no</a></code> a module)</p>
<a name="SYNOPSIS"></a><h1>SYNOPSIS</h1>
<pre class="verbatim"><ol><li>  <a class="l_k" href="functions/use.html">use</a> <a class="l_k" href="functions/if.html">if</a> <span class="w">CONDITION</span><span class="cm">,</span> <span class="w">MODULE</span> <span class="cm">=&gt;</span> <span class="w">ARGUMENTS</span><span class="sc">;</span></li><li>  <a class="l_k" href="functions/no.html">no</a> <a class="l_k" href="functions/if.html">if</a> <span class="w">CONDITION</span><span class="cm">,</span> <span class="w">MODULE</span> <span class="cm">=&gt;</span> <span class="w">ARGUMENTS</span><span class="sc">;</span></li></ol></pre><a name="DESCRIPTION"></a><h1>DESCRIPTION</h1>
<p>The <code class="inline">if</code>
 module is used to conditionally load or unload another module.
The construct</p>
<pre class="verbatim"><ol><li>  <a class="l_k" href="functions/use.html">use</a> if <span class="w">CONDITION</span><span class="cm">,</span> <span class="w">MODULE</span> <span class="cm">=&gt;</span> <span class="w">ARGUMENTS</span><span class="sc">;</span></li></ol></pre><p>will load MODULE only if CONDITION evaluates to true.
The above statement has no effect unless <code class="inline"><span class="w">CONDITION</span></code>
 is true.
If the CONDITION does evaluate to true, then the above line has
the same effect as:</p>
<pre class="verbatim"><ol><li>  <a class="l_k" href="functions/use.html">use</a> <span class="w">MODULE</span> <span class="w">ARGUMENTS</span><span class="sc">;</span></li></ol></pre><p>The use of <code class="inline"><span class="cm">=&gt;</span></code>
 above provides necessary quoting of <code class="inline"><span class="w">MODULE</span></code>
.
If you don't use the fat comma (eg you don't have any ARGUMENTS),
then you'll need to quote the MODULE.</p>
<a name="EXAMPLES"></a><h2>EXAMPLES</h2>
<p>The following line is taken from the testsuite for <a href="http://search.cpan.org/perldoc/File::Map">File::Map</a>:</p>
<pre class="verbatim"><ol><li>  <a class="l_k" href="functions/use.html">use</a> <a class="l_k" href="functions/if.html">if</a> <span class="i">$^O</span> <a class="l_k" href="functions/ne.html">ne</a> <span class="q">&#39;MSWin32&#39;</span><span class="cm">,</span> <span class="w">POSIX</span> <span class="cm">=&gt;</span> <span class="q">qw/setlocale LC_ALL/</span><span class="sc">;</span></li></ol></pre><p>If run on any operating system other than Windows,
this will import the functions <code class="inline"><span class="w">setlocale</span></code>
 and <code class="inline"><span class="w">LC_ALL</span></code>
 from <a href="POSIX.html">POSIX</a>.
On Windows it does nothing.</p>
<p>The following is used to <a href="deprecate.html">deprecate</a> core modules beyond a certain version of Perl:</p>
<pre class="verbatim"><ol><li>  <a class="l_k" href="functions/use.html">use</a> <a class="l_k" href="functions/if.html">if</a> <span class="i">$]</span> &gt; <span class="n">5.016</span><span class="cm">,</span> <span class="q">&#39;deprecate&#39;</span><span class="sc">;</span></li></ol></pre><p>This line is taken from <a href="http://search.cpan.org/perldoc/Text::Soundex">Text::Soundex</a> 3.04,
and marks it as deprecated beyond Perl 5.16.
If you <code class="inline"><a class="l_k" href="functions/use.html">use</a> <span class="w">Text::Soundex</span></code>
 in Perl 5.18, for example,
and you have used <a href="warnings.html">warnings</a>,
then you'll get a warning message
(the deprecate module looks to see whether the
calling module was <code class="inline"><a class="l_k" href="functions/use.html">use</a></code>'d from a core library directory,
and if so, generates a warning),
unless you've installed a more recent version of <a href="http://search.cpan.org/perldoc/Text::Soundex">Text::Soundex</a> from CPAN.</p>
<p>You can also specify to NOT use something:</p>
<pre class="verbatim"><ol><li> <a class="l_k" href="functions/no.html">no</a> <a class="l_k" href="functions/if.html">if</a> <span class="i">$]</span> <a class="l_k" href="functions/ge.html">ge</a> <span class="n">5.021_006</span><span class="cm">,</span> <span class="w">warnings</span> <span class="cm">=&gt;</span> <span class="q">&quot;locale&quot;</span><span class="sc">;</span></li></ol></pre><p>This warning category was added in the specified Perl version (a development
release).  Without the <code class="inline"><span class="q">&#39;if&#39;</span></code>
, trying to use it in an earlier release would
generate an unknown warning category error.</p>
<a name="BUGS"></a><h1>BUGS</h1>
<p>The current implementation does not allow specification of the
required version of the module.</p>
<a name="SEE-ALSO"></a><h1>SEE ALSO</h1>
<p><a href="http://search.cpan.org/perldoc/Module::Requires">Module::Requires</a> can be used to conditionally load one or modules,
with constraints based on the version of the module.
Unlike <code class="inline">if</code>
 though, <a href="http://search.cpan.org/perldoc/Module::Requires">Module::Requires</a> is not a core module.</p>
<p><a href="Module/Load/Conditional.html">Module::Load::Conditional</a> provides a number of functions you can use to
query what modules are available, and then load one or more of them at runtime.</p>
<p><a href="http://search.cpan.org/perldoc/provide">provide</a> can be used to select one of several possible modules to load,
based on what version of Perl is running.</p>
<a name="AUTHOR"></a><h1>AUTHOR</h1>
<p>Ilya Zakharevich <a href="mailto:ilyaz@cpan.org">mailto:ilyaz@cpan.org</a>.</p>
<a name="COPYRIGHT-AND-LICENCE"></a><h1>COPYRIGHT AND LICENCE</h1>
<p>This software is copyright (c) 2002 by Ilya Zakharevich.</p>
<p>This is free software; you can redistribute it and/or modify it under
the same terms as the Perl 5 programming language system itself.</p>




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  perldoc.setPath(0);
  perldoc.pageName    = 'if';
  perldoc.pageAddress = 'if.html';
  perldoc.contentPage = 1;
  explorePerl.render();
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</script>
    
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