CINXE.COM
unshift - 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>unshift - 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/unshift"> <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">5.16.0</a> <div class="dropdown-menu" aria-labelledby="dropdownlink-stable"> <a class="dropdown-item" href="/functions/unshift">Latest</a> <div class="dropdown-divider"></div> <a class="dropdown-item" href="/5.40.1/functions/unshift">5.40.1</a> <a class="dropdown-item" href="/5.40.0/functions/unshift">5.40.0</a> <div class="dropdown-divider"></div> <a class="dropdown-item" href="/5.38.3/functions/unshift">5.38.3</a> <a class="dropdown-item" href="/5.38.2/functions/unshift">5.38.2</a> <a class="dropdown-item" href="/5.38.1/functions/unshift">5.38.1</a> <a class="dropdown-item" href="/5.38.0/functions/unshift">5.38.0</a> <div class="dropdown-divider"></div> <a class="dropdown-item" href="/5.36.3/functions/unshift">5.36.3</a> <a class="dropdown-item" href="/5.36.2/functions/unshift">5.36.2</a> <a class="dropdown-item" href="/5.36.1/functions/unshift">5.36.1</a> <a class="dropdown-item" href="/5.36.0/functions/unshift">5.36.0</a> <div class="dropdown-divider"></div> <a class="dropdown-item" href="/5.34.3/functions/unshift">5.34.3</a> <a class="dropdown-item" href="/5.34.2/functions/unshift">5.34.2</a> <a class="dropdown-item" href="/5.34.1/functions/unshift">5.34.1</a> <a class="dropdown-item" href="/5.34.0/functions/unshift">5.34.0</a> <div class="dropdown-divider"></div> <a class="dropdown-item" href="/5.32.1/functions/unshift">5.32.1</a> <a class="dropdown-item" href="/5.32.0/functions/unshift">5.32.0</a> <div class="dropdown-divider"></div> <a class="dropdown-item" href="/5.30.3/functions/unshift">5.30.3</a> <a class="dropdown-item" href="/5.30.2/functions/unshift">5.30.2</a> <a class="dropdown-item" href="/5.30.1/functions/unshift">5.30.1</a> <a class="dropdown-item" href="/5.30.0/functions/unshift">5.30.0</a> <div class="dropdown-divider"></div> <a class="dropdown-item" href="/5.28.3/functions/unshift">5.28.3</a> <a class="dropdown-item" href="/5.28.2/functions/unshift">5.28.2</a> <a class="dropdown-item" href="/5.28.1/functions/unshift">5.28.1</a> <a class="dropdown-item" href="/5.28.0/functions/unshift">5.28.0</a> <div class="dropdown-divider"></div> <a class="dropdown-item" href="/5.26.3/functions/unshift">5.26.3</a> <a class="dropdown-item" href="/5.26.2/functions/unshift">5.26.2</a> <a class="dropdown-item" href="/5.26.1/functions/unshift">5.26.1</a> <a class="dropdown-item" href="/5.26.0/functions/unshift">5.26.0</a> <div class="dropdown-divider"></div> <a class="dropdown-item" href="/5.24.4/functions/unshift">5.24.4</a> <a class="dropdown-item" href="/5.24.3/functions/unshift">5.24.3</a> <a class="dropdown-item" href="/5.24.2/functions/unshift">5.24.2</a> <a class="dropdown-item" href="/5.24.1/functions/unshift">5.24.1</a> <a class="dropdown-item" href="/5.24.0/functions/unshift">5.24.0</a> <div class="dropdown-divider"></div> <a class="dropdown-item" href="/5.22.4/functions/unshift">5.22.4</a> <a class="dropdown-item" href="/5.22.3/functions/unshift">5.22.3</a> <a class="dropdown-item" href="/5.22.2/functions/unshift">5.22.2</a> <a class="dropdown-item" href="/5.22.1/functions/unshift">5.22.1</a> <a class="dropdown-item" href="/5.22.0/functions/unshift">5.22.0</a> <div class="dropdown-divider"></div> <a class="dropdown-item" href="/5.20.3/functions/unshift">5.20.3</a> <a class="dropdown-item" href="/5.20.2/functions/unshift">5.20.2</a> <a class="dropdown-item" href="/5.20.1/functions/unshift">5.20.1</a> <a class="dropdown-item" href="/5.20.0/functions/unshift">5.20.0</a> <div class="dropdown-divider"></div> <a class="dropdown-item" href="/5.18.4/functions/unshift">5.18.4</a> <a class="dropdown-item" href="/5.18.3/functions/unshift">5.18.3</a> <a class="dropdown-item" href="/5.18.2/functions/unshift">5.18.2</a> <a class="dropdown-item" href="/5.18.1/functions/unshift">5.18.1</a> <a class="dropdown-item" href="/5.18.0/functions/unshift">5.18.0</a> <div class="dropdown-divider"></div> <a class="dropdown-item" href="/5.16.3/functions/unshift">5.16.3</a> <a class="dropdown-item" href="/5.16.2/functions/unshift">5.16.2</a> <a class="dropdown-item" href="/5.16.1/functions/unshift">5.16.1</a> <a class="dropdown-item active" href="/5.16.0/functions/unshift">5.16.0</a> <div class="dropdown-divider"></div> <a class="dropdown-item" href="/5.14.4/functions/unshift">5.14.4</a> <a class="dropdown-item" href="/5.14.3/functions/unshift">5.14.3</a> <a class="dropdown-item" href="/5.14.2/functions/unshift">5.14.2</a> <a class="dropdown-item" href="/5.14.1/functions/unshift">5.14.1</a> <a class="dropdown-item" href="/5.14.0/functions/unshift">5.14.0</a> <div class="dropdown-divider"></div> <a class="dropdown-item" href="/5.12.5/functions/unshift">5.12.5</a> <a class="dropdown-item" href="/5.12.4/functions/unshift">5.12.4</a> <a class="dropdown-item" href="/5.12.3/functions/unshift">5.12.3</a> <a class="dropdown-item" href="/5.12.2/functions/unshift">5.12.2</a> <a class="dropdown-item" href="/5.12.1/functions/unshift">5.12.1</a> <a class="dropdown-item" href="/5.12.0/functions/unshift">5.12.0</a> <div class="dropdown-divider"></div> <a class="dropdown-item" href="/5.10.1/functions/unshift">5.10.1</a> <a class="dropdown-item" href="/5.10.0/functions/unshift">5.10.0</a> <div class="dropdown-divider"></div> <a class="dropdown-item" href="/5.8.9/functions/unshift">5.8.9</a> <a class="dropdown-item" href="/5.8.8/functions/unshift">5.8.8</a> <a class="dropdown-item" href="/5.8.7/functions/unshift">5.8.7</a> <a class="dropdown-item" href="/5.8.6/functions/unshift">5.8.6</a> <a class="dropdown-item" href="/5.8.5/functions/unshift">5.8.5</a> <a class="dropdown-item" href="/5.8.4/functions/unshift">5.8.4</a> <a class="dropdown-item" href="/5.8.3/functions/unshift">5.8.3</a> <a class="dropdown-item" href="/5.8.2/functions/unshift">5.8.2</a> <a class="dropdown-item" href="/5.8.1/functions/unshift">5.8.1</a> <a class="dropdown-item" href="/5.8.0/functions/unshift">5.8.0</a> <div class="dropdown-divider"></div> <a class="dropdown-item" href="/5.6.2/functions/unshift">5.6.2</a> <a class="dropdown-item" href="/5.6.1/functions/unshift">5.6.1</a> <a class="dropdown-item" href="/5.6.0/functions/unshift">5.6.0</a> <div class="dropdown-divider"></div> <a class="dropdown-item" href="/5.005_04/functions/unshift">5.005_04</a> <a class="dropdown-item" href="/5.005_03/functions/unshift">5.005_03</a> <a class="dropdown-item" href="/5.005_02/functions/unshift">5.005_02</a> <a class="dropdown-item" href="/5.005_01/functions/unshift">5.005_01</a> <a class="dropdown-item" href="/5.005/functions/unshift">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/unshift">blead</a> <a class="dropdown-item" href="/5.41.10/functions/unshift">5.41.10</a> <a class="dropdown-item" href="/5.41.9/functions/unshift">5.41.9</a> <a class="dropdown-item" href="/5.41.8/functions/unshift">5.41.8</a> <a class="dropdown-item" href="/5.41.7/functions/unshift">5.41.7</a> <a class="dropdown-item" href="/5.41.6/functions/unshift">5.41.6</a> <a class="dropdown-item" href="/5.41.5/functions/unshift">5.41.5</a> <a class="dropdown-item" href="/5.41.4/functions/unshift">5.41.4</a> <a class="dropdown-item" href="/5.41.3/functions/unshift">5.41.3</a> <a class="dropdown-item" href="/5.41.2/functions/unshift">5.41.2</a> <a class="dropdown-item" href="/5.41.1/functions/unshift">5.41.1</a> <div class="dropdown-divider"></div> <a class="dropdown-item" href="/5.40.1-RC1/functions/unshift">5.40.1-RC1</a> <a class="dropdown-item" href="/5.40.0-RC2/functions/unshift">5.40.0-RC2</a> <a class="dropdown-item" href="/5.40.0-RC1/functions/unshift">5.40.0-RC1</a> <div class="dropdown-divider"></div> <a class="dropdown-item" href="/5.39.10/functions/unshift">5.39.10</a> <a class="dropdown-item" href="/5.39.9/functions/unshift">5.39.9</a> <a class="dropdown-item" href="/5.39.8/functions/unshift">5.39.8</a> <a class="dropdown-item" href="/5.39.7/functions/unshift">5.39.7</a> <a class="dropdown-item" href="/5.39.6/functions/unshift">5.39.6</a> <a class="dropdown-item" href="/5.39.5/functions/unshift">5.39.5</a> <a class="dropdown-item" href="/5.39.4/functions/unshift">5.39.4</a> <a class="dropdown-item" href="/5.39.3/functions/unshift">5.39.3</a> <a class="dropdown-item" href="/5.39.2/functions/unshift">5.39.2</a> <a class="dropdown-item" href="/5.39.1/functions/unshift">5.39.1</a> <div class="dropdown-divider"></div> <a class="dropdown-item" href="/5.38.3-RC1/functions/unshift">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="/5.16.0/perl">Perl</a> <a class="dropdown-item" href="/5.16.0/perlintro">Intro</a> <a class="dropdown-item" href="/5.16.0/perl#Tutorials">Tutorials</a> <a class="dropdown-item" href="/5.16.0/perlfaq">FAQs</a> <a class="dropdown-item" href="/5.16.0/perl#Reference-Manual">Reference</a> <div class="dropdown-divider"></div> <a class="dropdown-item" href="/5.16.0/perlop">Operators</a> <a class="dropdown-item" href="/5.16.0/functions">Functions</a> <a class="dropdown-item" href="/5.16.0/variables">Variables</a> <a class="dropdown-item" href="/5.16.0/modules">Modules</a> <a class="dropdown-item" href="/5.16.0/perlutil">Utilities</a> <div class="dropdown-divider"></div> <a class="dropdown-item" href="/5.16.0/perldelta">Release Notes</a> <a class="dropdown-item" href="/5.16.0/perlcommunity">Community</a> <a class="dropdown-item" href="/5.16.0/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="/5.16.0/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="/5.16.0/functions">functions</a> / <a href="/5.16.0/functions/unshift">unshift</a> <div id="more"> (<a href="/5.16.0/functions/unshift.txt">source</a>, <a href="https://metacpan.org/pod/perlfunc#unshift-ARRAY,LIST">CPAN</a>) </div> </div> <div class="leading-notice"> You are viewing the version of this documentation from Perl 5.16.0. <a href="/functions/unshift">View the latest version</a> </div> <dl> <dt id="unshift-ARRAY,LIST"><a class="permalink" href="#unshift-ARRAY,LIST">#</a><a id="unshift"></a><a id="unshift-ARRAY-LIST"></a>unshift ARRAY,LIST </dt> <dd> </dd> <dt id="unshift-EXPR,LIST"><a class="permalink" href="#unshift-EXPR,LIST">#</a><a id="unshift1"></a><a id="unshift-EXPR-LIST"></a>unshift EXPR,LIST</dt> <dd> <p>Does the opposite of a <code>shift</code>. Or the opposite of a <code>push</code>, depending on how you look at it. Prepends list to the front of the array and returns the new number of elements in the array.</p> <pre><code>unshift(@ARGV, '-e') unless $ARGV[0] =~ /^-/;</code></pre> <p>Note the LIST is prepended whole, not one element at a time, so the prepended elements stay in the same order. Use <code>reverse</code> to do the reverse.</p> <p>Starting with Perl 5.14, <code>unshift</code> can take a scalar EXPR, which must hold a reference to an unblessed array. The argument will be dereferenced automatically. This aspect of <code>unshift</code> is considered highly experimental. The exact behaviour may change in a future version of Perl.</p> <p>To avoid confusing would-be users of your code who are running earlier versions of Perl with mysterious syntax errors, put this sort of thing at the top of your file to signal that your code will work <i>only</i> on Perls of a recent vintage:</p> <pre><code>use 5.014; # so push/pop/etc work on scalars (experimental)</code></pre> </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>