CINXE.COM
use - Perldoc Browser
<!DOCTYPE html> <html lang="en"> <head> <meta charset="utf-8"> <meta http-equiv="X-UA-Compatible" content="IE=edge"> <meta name="viewport" content="width=device-width, initial-scale=1"> <title>use - Perldoc Browser</title> <link rel="search" href="/opensearch.xml" type="application/opensearchdescription+xml" title="Perldoc Browser"> <link rel="canonical" href="https://perldoc.perl.org/functions/use"> <link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.5.2/css/bootstrap.min.css" integrity="sha384-JcKb8q3iqJ61gNV9KGb8thSsNjpSL0n8PARn9HuZOnIxN0hoP+VmmDGMN5t9UJ0Z" crossorigin="anonymous"> <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/highlight.js/10.5.0/styles/stackoverflow-light.min.css" integrity="sha512-cG1IdFxqipi3gqLmksLtuk13C+hBa57a6zpWxMeoY3Q9O6ooFxq50DayCdm0QrDgZjMUn23z/0PMZlgft7Yp5Q==" crossorigin="anonymous" /> <style> body { background: #f4f4f5; color: #020202; } .navbar-dark { background-image: -webkit-linear-gradient(top, #005f85 0, #002e49 100%); background-image: -o-linear-gradient(top, #005f85 0, #002e49 100%); background-image: linear-gradient(to bottom, #005f85 0, #002e49 100%); filter: progid:DXImageTransform.Microsoft.gradient(startColorstr='#ff005f85', endColorstr='#ff002e49', GradientType=0); background-repeat: repeat-x; } .navbar-dark .navbar-nav .nav-link, .navbar-dark .navbar-nav .nav-link:focus { color: #fff } .navbar-dark .navbar-nav .nav-link:hover { color: #ffef68 } #wrapperlicious { margin: 0 auto; font: 0.9em 'Helvetica Neue', Helvetica, sans-serif; font-weight: normal; line-height: 1.5em; margin: 0; padding: 0; } #wrapperlicious h1 { font-size: 1.5em } #wrapperlicious h2 { font-size: 1.3em } #wrapperlicious h3 { font-size: 1.1em } #wrapperlicious h4 { font-size: 0.9em } #wrapperlicious h1, #wrapperlicious h2, #wrapperlicious h3, #wrapperlicious h4, #wrapperlicious dt { color: #020202; margin-top: 1em; margin-bottom: 1em; position: relative; font-weight: bold; } #wrapperlicious a { color: inherit; text-decoration: underline } #wrapperlicious #toc { text-decoration: none } #wrapperlicious a:hover { color: #2a2a2a } #wrapperlicious a img { border: 0 } #wrapperlicious :not(pre) > code { color: inherit; background-color: rgba(0, 0, 0, 0.04); border-radius: 3px; font: 0.9em Consolas, Menlo, Monaco, monospace; padding: 0.3em; } #wrapperlicious dd { margin: 0; margin-left: 2em; } #wrapperlicious dt { color: #2a2a2a; font-weight: bold; margin-left: 0.9em; } #wrapperlicious p { margin-bottom: 1em; margin-top: 1em; } #wrapperlicious li > p { margin-bottom: 0; margin-top: 0; } #wrapperlicious pre { border: 1px solid #c1c1c1; border-radius: 3px; font: 100% Consolas, Menlo, Monaco, monospace; margin-bottom: 1em; margin-top: 1em; } #wrapperlicious pre > code { display: block; background-color: #f6f6f6; font: 0.9em Consolas, Menlo, Monaco, monospace; line-height: 1.5em; text-align: left; white-space: pre; padding: 1em; } #wrapperlicious dl, #wrapperlicious ol, #wrapperlicious ul { margin-bottom: 1em; margin-top: 1em; } #wrapperlicious ul { list-style-type: square; } #wrapperlicious ul ul { margin-bottom: 0px; margin-top: 0px; } #footer { font-size: 0.8em; padding-top: 0.5em; text-align: center; } #more { display: inline; font-size: 0.8em; } #perldocdiv { background-color: #fff; border: 1px solid #c1c1c1; border-bottom-left-radius: 5px; border-bottom-right-radius: 5px; margin-left: auto; margin-right: auto; padding: 3em; padding-top: 1em; max-width: 960px; } #moduleversion { float: right } #wrapperlicious .leading-notice { font-style: italic; padding-left: 1em; margin-top: 1em; margin-bottom: 1em; } #wrapperlicious .permalink { display: none; left: -0.75em; position: absolute; padding-right: 0.25em; text-decoration: none; } #wrapperlicious h1:hover .permalink, #wrapperlicious h2:hover .permalink, #wrapperlicious h3:hover .permalink, #wrapperlicious h4:hover .permalink, #wrapperlicious dt:hover .permalink { display: block; } </style> <!-- Global site tag (gtag.js) - Google Analytics --> <script async src="https://www.googletagmanager.com/gtag/js?id=G-KVNWBNT5FB"></script> <script> window.dataLayer = window.dataLayer || []; function gtag(){dataLayer.push(arguments);} gtag('js', new Date()); gtag('config', 'G-KVNWBNT5FB'); gtag('config', 'UA-50555-3'); </script> </head> <body> <nav class="navbar navbar-expand-md navbar-dark bg-dark justify-content-between"> <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarNav" aria-controls="navbarNav" aria-expanded="false" aria-label="Toggle navigation"> <span class="navbar-toggler-icon"></span> </button> <a class="navbar-brand" href="/"><img src="/images/perl_camel_30.png" width="30" height="30" class="d-inline-block align-top" alt="Perl Camel Logo"> Perldoc Browser</a> <div class="collapse navbar-collapse" id="navbarNav"> <ul class="navbar-nav mr-auto"> <li class="nav-item dropdown text-nowrap"> <a class="nav-link dropdown-toggle" href="#" id="dropdownlink-stable" role="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">5.40.1</a> <div class="dropdown-menu" aria-labelledby="dropdownlink-stable"> <a class="dropdown-item" href="/functions/use">Latest</a> <div class="dropdown-divider"></div> <a class="dropdown-item active" href="/5.40.1/functions/use">5.40.1</a> <a class="dropdown-item" href="/5.40.0/functions/use">5.40.0</a> <div class="dropdown-divider"></div> <a class="dropdown-item" href="/5.38.3/functions/use">5.38.3</a> <a class="dropdown-item" href="/5.38.2/functions/use">5.38.2</a> <a class="dropdown-item" href="/5.38.1/functions/use">5.38.1</a> <a class="dropdown-item" href="/5.38.0/functions/use">5.38.0</a> <div class="dropdown-divider"></div> <a class="dropdown-item" href="/5.36.3/functions/use">5.36.3</a> <a class="dropdown-item" href="/5.36.2/functions/use">5.36.2</a> <a class="dropdown-item" href="/5.36.1/functions/use">5.36.1</a> <a class="dropdown-item" href="/5.36.0/functions/use">5.36.0</a> <div class="dropdown-divider"></div> <a class="dropdown-item" href="/5.34.3/functions/use">5.34.3</a> <a class="dropdown-item" href="/5.34.2/functions/use">5.34.2</a> <a class="dropdown-item" href="/5.34.1/functions/use">5.34.1</a> <a class="dropdown-item" href="/5.34.0/functions/use">5.34.0</a> <div class="dropdown-divider"></div> <a class="dropdown-item" href="/5.32.1/functions/use">5.32.1</a> <a class="dropdown-item" href="/5.32.0/functions/use">5.32.0</a> <div class="dropdown-divider"></div> <a class="dropdown-item" href="/5.30.3/functions/use">5.30.3</a> <a class="dropdown-item" href="/5.30.2/functions/use">5.30.2</a> <a class="dropdown-item" href="/5.30.1/functions/use">5.30.1</a> <a class="dropdown-item" href="/5.30.0/functions/use">5.30.0</a> <div class="dropdown-divider"></div> <a class="dropdown-item" href="/5.28.3/functions/use">5.28.3</a> <a class="dropdown-item" href="/5.28.2/functions/use">5.28.2</a> <a class="dropdown-item" href="/5.28.1/functions/use">5.28.1</a> <a class="dropdown-item" href="/5.28.0/functions/use">5.28.0</a> <div class="dropdown-divider"></div> <a class="dropdown-item" href="/5.26.3/functions/use">5.26.3</a> <a class="dropdown-item" href="/5.26.2/functions/use">5.26.2</a> <a class="dropdown-item" href="/5.26.1/functions/use">5.26.1</a> <a class="dropdown-item" href="/5.26.0/functions/use">5.26.0</a> <div class="dropdown-divider"></div> <a class="dropdown-item" href="/5.24.4/functions/use">5.24.4</a> <a class="dropdown-item" href="/5.24.3/functions/use">5.24.3</a> <a class="dropdown-item" href="/5.24.2/functions/use">5.24.2</a> <a class="dropdown-item" href="/5.24.1/functions/use">5.24.1</a> <a class="dropdown-item" href="/5.24.0/functions/use">5.24.0</a> <div class="dropdown-divider"></div> <a class="dropdown-item" href="/5.22.4/functions/use">5.22.4</a> <a class="dropdown-item" href="/5.22.3/functions/use">5.22.3</a> <a class="dropdown-item" href="/5.22.2/functions/use">5.22.2</a> <a class="dropdown-item" href="/5.22.1/functions/use">5.22.1</a> <a class="dropdown-item" href="/5.22.0/functions/use">5.22.0</a> <div class="dropdown-divider"></div> <a class="dropdown-item" href="/5.20.3/functions/use">5.20.3</a> <a class="dropdown-item" href="/5.20.2/functions/use">5.20.2</a> <a class="dropdown-item" href="/5.20.1/functions/use">5.20.1</a> <a class="dropdown-item" href="/5.20.0/functions/use">5.20.0</a> <div class="dropdown-divider"></div> <a class="dropdown-item" href="/5.18.4/functions/use">5.18.4</a> <a class="dropdown-item" href="/5.18.3/functions/use">5.18.3</a> <a class="dropdown-item" href="/5.18.2/functions/use">5.18.2</a> <a class="dropdown-item" href="/5.18.1/functions/use">5.18.1</a> <a class="dropdown-item" href="/5.18.0/functions/use">5.18.0</a> <div class="dropdown-divider"></div> <a class="dropdown-item" href="/5.16.3/functions/use">5.16.3</a> <a class="dropdown-item" href="/5.16.2/functions/use">5.16.2</a> <a class="dropdown-item" href="/5.16.1/functions/use">5.16.1</a> <a class="dropdown-item" href="/5.16.0/functions/use">5.16.0</a> <div class="dropdown-divider"></div> <a class="dropdown-item" href="/5.14.4/functions/use">5.14.4</a> <a class="dropdown-item" href="/5.14.3/functions/use">5.14.3</a> <a class="dropdown-item" href="/5.14.2/functions/use">5.14.2</a> <a class="dropdown-item" href="/5.14.1/functions/use">5.14.1</a> <a class="dropdown-item" href="/5.14.0/functions/use">5.14.0</a> <div class="dropdown-divider"></div> <a class="dropdown-item" href="/5.12.5/functions/use">5.12.5</a> <a class="dropdown-item" href="/5.12.4/functions/use">5.12.4</a> <a class="dropdown-item" href="/5.12.3/functions/use">5.12.3</a> <a class="dropdown-item" href="/5.12.2/functions/use">5.12.2</a> <a class="dropdown-item" href="/5.12.1/functions/use">5.12.1</a> <a class="dropdown-item" href="/5.12.0/functions/use">5.12.0</a> <div class="dropdown-divider"></div> <a class="dropdown-item" href="/5.10.1/functions/use">5.10.1</a> <a class="dropdown-item" href="/5.10.0/functions/use">5.10.0</a> <div class="dropdown-divider"></div> <a class="dropdown-item" href="/5.8.9/functions/use">5.8.9</a> <a class="dropdown-item" href="/5.8.8/functions/use">5.8.8</a> <a class="dropdown-item" href="/5.8.7/functions/use">5.8.7</a> <a class="dropdown-item" href="/5.8.6/functions/use">5.8.6</a> <a class="dropdown-item" href="/5.8.5/functions/use">5.8.5</a> <a class="dropdown-item" href="/5.8.4/functions/use">5.8.4</a> <a class="dropdown-item" href="/5.8.3/functions/use">5.8.3</a> <a class="dropdown-item" href="/5.8.2/functions/use">5.8.2</a> <a class="dropdown-item" href="/5.8.1/functions/use">5.8.1</a> <a class="dropdown-item" href="/5.8.0/functions/use">5.8.0</a> <div class="dropdown-divider"></div> <a class="dropdown-item" href="/5.6.2/functions/use">5.6.2</a> <a class="dropdown-item" href="/5.6.1/functions/use">5.6.1</a> <a class="dropdown-item" href="/5.6.0/functions/use">5.6.0</a> <div class="dropdown-divider"></div> <a class="dropdown-item" href="/5.005_04/functions/use">5.005_04</a> <a class="dropdown-item" href="/5.005_03/functions/use">5.005_03</a> <a class="dropdown-item" href="/5.005_02/functions/use">5.005_02</a> <a class="dropdown-item" href="/5.005_01/functions/use">5.005_01</a> <a class="dropdown-item" href="/5.005/functions/use">5.005</a> </div> </li> <li class="nav-item dropdown text-nowrap"> <a class="nav-link dropdown-toggle" href="#" id="dropdownlink-dev" role="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">Dev</a> <div class="dropdown-menu" aria-labelledby="dropdownlink-dev"> <a class="dropdown-item" href="/blead/functions/use">blead</a> <a class="dropdown-item" href="/5.41.9/functions/use">5.41.9</a> <a class="dropdown-item" href="/5.41.8/functions/use">5.41.8</a> <a class="dropdown-item" href="/5.41.7/functions/use">5.41.7</a> <a class="dropdown-item" href="/5.41.6/functions/use">5.41.6</a> <a class="dropdown-item" href="/5.41.5/functions/use">5.41.5</a> <a class="dropdown-item" href="/5.41.4/functions/use">5.41.4</a> <a class="dropdown-item" href="/5.41.3/functions/use">5.41.3</a> <a class="dropdown-item" href="/5.41.2/functions/use">5.41.2</a> <a class="dropdown-item" href="/5.41.1/functions/use">5.41.1</a> <div class="dropdown-divider"></div> <a class="dropdown-item" href="/5.40.1-RC1/functions/use">5.40.1-RC1</a> <a class="dropdown-item" href="/5.40.0-RC2/functions/use">5.40.0-RC2</a> <a class="dropdown-item" href="/5.40.0-RC1/functions/use">5.40.0-RC1</a> <div class="dropdown-divider"></div> <a class="dropdown-item" href="/5.39.10/functions/use">5.39.10</a> <a class="dropdown-item" href="/5.39.9/functions/use">5.39.9</a> <a class="dropdown-item" href="/5.39.8/functions/use">5.39.8</a> <a class="dropdown-item" href="/5.39.7/functions/use">5.39.7</a> <a class="dropdown-item" href="/5.39.6/functions/use">5.39.6</a> <a class="dropdown-item" href="/5.39.5/functions/use">5.39.5</a> <a class="dropdown-item" href="/5.39.4/functions/use">5.39.4</a> <a class="dropdown-item" href="/5.39.3/functions/use">5.39.3</a> <a class="dropdown-item" href="/5.39.2/functions/use">5.39.2</a> <a class="dropdown-item" href="/5.39.1/functions/use">5.39.1</a> <div class="dropdown-divider"></div> <a class="dropdown-item" href="/5.38.3-RC1/functions/use">5.38.3-RC1</a> </div> </li> <li class="nav-item dropdown text-nowrap"> <a class="nav-link dropdown-toggle" href="#" id="dropdownlink-nav" role="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">Documentation</a> <div class="dropdown-menu" aria-labelledby="dropdownlink-nav"> <a class="dropdown-item" href="/5.40.1/perl">Perl</a> <a class="dropdown-item" href="/5.40.1/perlintro">Intro</a> <a class="dropdown-item" href="/5.40.1/perl#Tutorials">Tutorials</a> <a class="dropdown-item" href="/5.40.1/perlfaq">FAQs</a> <a class="dropdown-item" href="/5.40.1/perl#Reference-Manual">Reference</a> <div class="dropdown-divider"></div> <a class="dropdown-item" href="/5.40.1/perlop">Operators</a> <a class="dropdown-item" href="/5.40.1/functions">Functions</a> <a class="dropdown-item" href="/5.40.1/variables">Variables</a> <a class="dropdown-item" href="/5.40.1/modules">Modules</a> <a class="dropdown-item" href="/5.40.1/perlutil">Utilities</a> <div class="dropdown-divider"></div> <a class="dropdown-item" href="/5.40.1/perldelta">Release Notes</a> <a class="dropdown-item" href="/5.40.1/perlcommunity">Community</a> <a class="dropdown-item" href="/5.40.1/perlhist">History</a> </div> </li> </ul> <ul class="navbar-nav"> <script> function set_expand (expand) { var perldocdiv = document.getElementById('perldocdiv'); var width = window.getComputedStyle(perldocdiv).getPropertyValue('max-width'); var expanded = (width == '' || width == 'none') ? true : false; if (expand === null) { expand = !expanded; } if ((expand && !expanded) || (!expand && expanded)) { perldocdiv.style.setProperty('max-width', expand ? 'none' : '960px'); var button_classlist = document.getElementById('content-expand-button').classList; if (expand) { button_classlist.add('btn-light'); button_classlist.remove('btn-outline-light'); } else { button_classlist.add('btn-outline-light'); button_classlist.remove('btn-light'); } } return expand; } function toggle_expand () { var expand = set_expand(null); document.cookie = 'perldoc_expand=' + (expand ? 1 : 0) + '; path=/; expires=Tue, 19 Jan 2038 03:14:07 UTC'; } function read_expand () { return document.cookie.split(';').some(function (item) { return item.indexOf('perldoc_expand=1') >= 0 }); } if (document.readyState === 'loading') { document.addEventListener('DOMContentLoaded', function () { if (read_expand()) { set_expand(true); } }); } else if (read_expand()) { set_expand(true); } </script> <button id="content-expand-button" type="button" class="btn btn-outline-light d-none d-lg-inline-block mr-4" onclick="toggle_expand()">Expand</button> </ul> <form class="form-inline" method="get" action="/5.40.1/search"> <input class="form-control mr-3" type="search" name="q" placeholder="Search" aria-label="Search" value=""> </form> </div> </nav> <div id="wrapperlicious" class="container-fluid"> <div id="perldocdiv"> <div id="links"> <a href="/5.40.1/functions">functions</a> / <a href="/5.40.1/functions/use">use</a> <div id="more"> (<a href="/5.40.1/functions/use.txt">source</a>, <a href="https://metacpan.org/pod/perlfunc#use-Module-VERSION-LIST">CPAN</a>) </div> </div> <div class="leading-notice"> You are viewing the version of this documentation from Perl 5.40.1. <a href="/functions/use">View the latest version</a> </div> <dl> <dt id="use-Module-VERSION-LIST"><a class="permalink" href="#use-Module-VERSION-LIST">#</a><a id="use"></a>use Module VERSION LIST </dt> <dd> </dd> <dt id="use-Module-VERSION"><a class="permalink" href="#use-Module-VERSION">#</a><a id="use1"></a>use Module VERSION</dt> <dd> </dd> <dt id="use-Module-LIST"><a class="permalink" href="#use-Module-LIST">#</a><a id="use2"></a>use Module LIST</dt> <dd> </dd> <dt id="use-Module"><a class="permalink" href="#use-Module">#</a><a id="use3"></a>use Module</dt> <dd> <p>Imports some semantics into the current package from the named module, generally by aliasing certain subroutine or variable names into your package. It is exactly equivalent to</p> <pre><code>BEGIN { require Module; Module->import( LIST ); }</code></pre> <p>except that Module <i>must</i> be a bareword. The importation can be made conditional by using the <a href="/5.40.1/if">if</a> module.</p> <p>The <code>BEGIN</code> forces the <a href="/5.40.1/functions/require"><code>require</code></a> and <a href="/5.40.1/functions/import"><code>import</code></a> to happen at compile time. The <a href="/5.40.1/functions/require"><code>require</code></a> makes sure the module is loaded into memory if it hasn't been yet. The <a href="/5.40.1/functions/import"><code>import</code></a> is not a builtin; it's just an ordinary static method call into the <code>Module</code> package to tell the module to import the list of features back into the current package. The module can implement its <a href="/5.40.1/functions/import"><code>import</code></a> method any way it likes, though most modules just choose to derive their <a href="/5.40.1/functions/import"><code>import</code></a> method via inheritance from the <code>Exporter</code> class that is defined in the <a href="/5.40.1/Exporter"><code>Exporter</code></a> module. See <a href="/5.40.1/Exporter">Exporter</a>. If no <a href="/5.40.1/functions/import"><code>import</code></a> method can be found, then the call is skipped, even if there is an AUTOLOAD method.</p> <p>If you do not want to call the package's <a href="/5.40.1/functions/import"><code>import</code></a> method (for instance, to stop your namespace from being altered), explicitly supply the empty list:</p> <pre><code>use Module ();</code></pre> <p>That is exactly equivalent to</p> <pre><code class="plaintext">BEGIN { require Module }</code></pre> <p>If the VERSION argument is present between Module and LIST, then the <a href="/5.40.1/functions/use"><code>use</code></a> will call the <code>VERSION</code> method in class Module with the given version as an argument:</p> <pre><code>use Module 12.34;</code></pre> <p>is equivalent to:</p> <pre><code>BEGIN { require Module; Module->VERSION(12.34) }</code></pre> <p>The <a href="/5.40.1/UNIVERSAL#VERSION-(-%5B-REQUIRE-%5D-)">default <code>VERSION</code> method</a>, inherited from the <a href="/5.40.1/UNIVERSAL"><code>UNIVERSAL</code></a> class, croaks if the given version is larger than the value of the variable <code>$Module::VERSION</code>.</p> <p>The VERSION argument cannot be an arbitrary expression. It only counts as a VERSION argument if it is a version number literal, starting with either a digit or <code>v</code> followed by a digit. Anything that doesn't look like a version literal will be parsed as the start of the LIST. Nevertheless, many attempts to use an arbitrary expression as a VERSION argument will appear to work, because <a href="/5.40.1/Exporter">Exporter</a>'s <code>import</code> method handles numeric arguments specially, performing version checks rather than treating them as things to export.</p> <p>Again, there is a distinction between omitting LIST (<a href="/5.40.1/functions/import"><code>import</code></a> called with no arguments) and an explicit empty LIST <code>()</code> (<a href="/5.40.1/functions/import"><code>import</code></a> not called). Note that there is no comma after VERSION!</p> <p>Because this is a wide-open interface, pragmas (compiler directives) are also implemented this way. Some of the currently implemented pragmas are:</p> <pre><code>use constant; use diagnostics; use integer; use sigtrap qw(SEGV BUS); use strict qw(subs vars refs); use subs qw(afunc blurfl); use warnings qw(all); use sort qw(stable);</code></pre> <p>Some of these pseudo-modules import semantics into the current block scope (like <a href="/5.40.1/strict"><code>strict</code></a> or <a href="/5.40.1/integer"><code>integer</code></a>, unlike ordinary modules, which import symbols into the current package (which are effective through the end of the file).</p> <p>Because <a href="/5.40.1/functions/use"><code>use</code></a> takes effect at compile time, it doesn't respect the ordinary flow control of the code being compiled. In particular, putting a <a href="/5.40.1/functions/use"><code>use</code></a> inside the false branch of a conditional doesn't prevent it from being processed. If a module or pragma only needs to be loaded conditionally, this can be done using the <a href="/5.40.1/if">if</a> pragma:</p> <pre><code>use if $] < 5.008, "utf8"; use if WANT_WARNINGS, warnings => qw(all);</code></pre> <p>There's a corresponding <a href="/5.40.1/functions/no"><code>no</code></a> declaration that unimports meanings imported by <a href="/5.40.1/functions/use"><code>use</code></a>, i.e., it calls <code>Module->unimport(LIST)</code> instead of <a href="/5.40.1/functions/import"><code>import</code></a>. It behaves just as <a href="/5.40.1/functions/import"><code>import</code></a> does with VERSION, an omitted or empty LIST, or no unimport method being found.</p> <pre><code>no integer; no strict 'refs'; no warnings;</code></pre> <p>See <a href="/5.40.1/perlmodlib">perlmodlib</a> for a list of standard modules and pragmas. See <a href="/5.40.1/perlrun#-m%5B-%5Dmodule">perlrun</a> for the <code>-M</code> and <code>-m</code> command-line options to Perl that give <a href="/5.40.1/functions/use"><code>use</code></a> functionality from the command-line.</p> </dd> <dt id="use-VERSION"><a class="permalink" href="#use-VERSION">#</a><a id="use4"></a>use VERSION</dt> <dd> <p>Lexically enables all features available in the requested version as defined by the <a href="/5.40.1/feature">feature</a> pragma, disabling any features not in the requested version's feature bundle. See <a href="/5.40.1/feature">feature</a>.</p> <p>VERSION may be either a v-string such as v5.24.1, which will be compared to <a href="/5.40.1/perlvar#%24%5EV"><code>$^V</code></a> (aka $PERL_VERSION), or a numeric argument of the form 5.024001, which will be compared to <a href="/5.40.1/perlvar#%24%5D"><code>$]</code></a>. An exception is raised if VERSION is greater than the version of the current Perl interpreter; Perl will not attempt to parse the rest of the file. Compare with <a href="/5.40.1/functions/require"><code>require</code></a>, which can do a similar check at run time.</p> <p>If the specified Perl version is 5.12 or higher, strictures are enabled lexically as with <a href="/5.40.1/strict"><code>use strict</code></a>.</p> <p>If the specified Perl version is 5.35.0 or higher, <a href="/5.40.1/warnings">warnings</a> are enabled.</p> <p>If the specified Perl version is 5.39.0 or higher, builtin functions are imported lexically as with <a href="/5.40.1/builtin"><code>use builtin</code></a> with a corresponding version bundle.</p> <p>Use of <code>use VERSION</code> while another is in effect is not allowed with a <code>use v5.39;</code> or greater version. For lower versions, <code>use VERSION</code> will override most behavior of a previous <code>use VERSION</code>, possibly removing <code>warnings</code> and <code>feature</code> effects added by it. This behavior is deprecated, and a future release of perl will disallow changing the version once one has been declared. Additionally, a <code>use VERSION</code> with a version less than 5.11 is not allowed after a <code>use VERSION</code> with a version greater than 5.11.</p> <p><code>use VERSION</code> does not load the <i>feature.pm</i>, <i>strict.pm</i>, <i>warnings.pm</i> or <i>builtin.pm</i> files, but instead implements the equivalent functionality directly.</p> <p>In the current implementation, any explicit use of <code>no strict</code> overrides <code>use VERSION</code>, even if it comes before it. However, this may be subject to change in a future release of Perl, so new code should not rely on this fact. It is recommended that a <code>use VERSION</code> declaration be the first significant statement within a file (possibly after a <code>package</code> statement or any amount of whitespace or comment), so that its effects happen first, and other pragmata are applied after it.</p> <p>Specifying VERSION as a numeric argument of the form 5.024001 should generally be avoided as older less readable syntax compared to v5.24.1. Before perl 5.8.0 released in 2002 the more verbose numeric form was the only supported syntax, which is why you might see it in older code.</p> <pre><code>use v5.24.1; # compile time version check use 5.24.1; # ditto use 5.024_001; # ditto; older syntax compatible with perl 5.6</code></pre> <p>This is often useful if you need to check the current Perl version before <a href="/5.40.1/functions/use"><code>use</code></a>ing library modules that won't work with older versions of Perl. (We try not to do this more than we have to.)</p> <p>Symmetrically, <code>no VERSION</code> allows you to specify that you want a version of Perl older than the specified one. Historically this was added during early designs of the Raku language (formerly "Perl 6"), so that a Perl 5 program could begin</p> <pre><code>no 6;</code></pre> <p>to declare that it is not a Perl 6 program. As the two languages have different implementations, file naming conventions, and other infrastructure, this feature is now little used in practice and should be avoided in newly-written code.</p> <p>Care should be taken when using the <code>no VERSION</code> form, as it is <i>only</i> meant to be used to assert that the running Perl is of a earlier version than its argument and <i>not</i> to undo the feature-enabling side effects of <code>use VERSION</code>.</p> </dd> </dl> </div> <div id="footer"> <p>Perldoc Browser is maintained by Dan Book (<a href="https://metacpan.org/author/DBOOK">DBOOK</a>). Please contact him via the <a href="https://github.com/Grinnz/perldoc-browser/issues">GitHub issue tracker</a> or <a href="mailto:dbook@cpan.org">email</a> regarding any issues with the site itself, search, or rendering of documentation.</p> <p>The Perl documentation is maintained by the Perl 5 Porters in the development of Perl. Please contact them via the <a href="https://github.com/Perl/perl5/issues">Perl issue tracker</a>, the <a href="https://lists.perl.org/list/perl5-porters.html">mailing list</a>, or <a href="https://kiwiirc.com/client/irc.perl.org/p5p">IRC</a> to report any issues with the contents or format of the documentation.</p> </div> </div> <script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.5.1/jquery.slim.min.js" integrity="sha512-/DXTXr6nQodMUiq+IUJYCt2PPOUjrHJ9wFrqpJ3XkgPNOZVfMok7cRw6CSxyCQxXn6ozlESsSh1/sMCTF1rL/g==" crossorigin="anonymous"></script> <script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.16.1/umd/popper.min.js" integrity="sha512-ubuT8Z88WxezgSqf3RLuNi5lmjstiJcyezx34yIU2gAHonIi27Na7atqzUZCOoY4CExaoFumzOsFQ2Ch+I/HCw==" crossorigin="anonymous"></script> <script src="https://stackpath.bootstrapcdn.com/bootstrap/4.5.2/js/bootstrap.min.js" integrity="sha384-B4gt1jrGC7Jh4AgTPSdUtOBvfO8shuf57BaghqFfPlYxofvL8/KUEfYiJOMMV+rV" crossorigin="anonymous"></script> <script src="/js/highlight.pack.js"></script> <script>hljs.highlightAll();</script> </body> </html>