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<ul><li><a href="#NAME">NAME</a><li><a href="#SYNOPSIS">SYNOPSIS</a><li><a href="#DESCRIPTION">DESCRIPTION</a><ul><li><a href="#Lexical-effect">Lexical effect</a><li><a href="#no-feature">no feature</a></ul><li><a href="#AVAILABLE-FEATURES">AVAILABLE FEATURES</a><ul><li><a href="#The-'say'-feature">The 'say' feature</a><li><a href="#The-'state'-feature">The 'state' feature</a><li><a href="#The-'switch'-feature">The 'switch' feature</a><li><a href="#The-'unicode_strings'-feature">The 'unicode_strings' feature</a><li><a href="#The-'unicode_eval'-and-'evalbytes'-features">The 'unicode_eval' and 'evalbytes' features</a><li><a href="#The-'current_sub'-feature">The 'current_sub' feature</a><li><a href="#The-'array_base'-feature">The 'array_base' feature</a><li><a href="#The-'fc'-feature">The 'fc' feature</a><li><a href="#The-'lexical_subs'-feature">The 'lexical_subs' feature</a><li><a href="#The-'postderef'-and-'postderef_qq'-features">The 'postderef' and 'postderef_qq' features</a><li><a href="#The-'signatures'-feature">The 'signatures' feature</a><li><a href="#The-'refaliasing'-feature">The 'refaliasing' feature</a><li><a href="#The-'bitwise'-feature">The 'bitwise' feature</a><li><a href="#The-'declared_refs'-feature">The 'declared_refs' feature</a></ul><li><a href="#FEATURE-BUNDLES">FEATURE BUNDLES</a><li><a href="#IMPLICIT-LOADING">IMPLICIT LOADING</a></ul><a name="NAME"></a><h1>NAME</h1>
<p>feature - Perl pragma to enable new features</p>
<a name="SYNOPSIS"></a><h1>SYNOPSIS</h1>
<pre class="verbatim"><ol><li>    <a class="l_k" href="functions/use.html">use</a> <span class="w">feature</span> <span class="q">qw(say switch)</span><span class="sc">;</span></li><li>    <a class="l_k" href="functions/given.html">given</a> <span class="s">(</span><span class="i">$foo</span><span class="s">)</span> <span class="s">{</span></li><li>        <a class="l_k" href="functions/when.html">when</a> <span class="s">(</span><span class="n">1</span><span class="s">)</span>          <span class="s">{</span> <a class="l_k" href="functions/say.html">say</a> <span class="q">&quot;\$foo == 1&quot;</span> <span class="s">}</span></li><li>        <a class="l_k" href="functions/when.html">when</a> <span class="s">(</span><span class="s">[</span><span class="n">2</span><span class="cm">,</span><span class="n">3</span><span class="s">]</span><span class="s">)</span>      <span class="s">{</span> <a class="l_k" href="functions/say.html">say</a> <span class="q">&quot;\$foo == 2 || \$foo == 3&quot;</span> <span class="s">}</span></li><li>        <a class="l_k" href="functions/when.html">when</a> <span class="s">(</span><span class="q">/^a[bc]d$/</span><span class="s">)</span> <span class="s">{</span> <a class="l_k" href="functions/say.html">say</a> <span class="q">&quot;\$foo eq &#39;abd&#39; || \$foo eq &#39;acd&#39;&quot;</span> <span class="s">}</span></li><li>        <a class="l_k" href="functions/when.html">when</a> <span class="s">(</span><span class="i">$_</span> &gt; <span class="n">100</span><span class="s">)</span>   <span class="s">{</span> <a class="l_k" href="functions/say.html">say</a> <span class="q">&quot;\$foo &gt; 100&quot;</span> <span class="s">}</span></li><li>        <span class="i">default</span>           <span class="s">{</span> <a class="l_k" href="functions/say.html">say</a> <span class="q">&quot;None of the above&quot;</span> <span class="s">}</span></li><li>    <span class="s">}</span></li><li></li><li>    <a class="l_k" href="functions/use.html">use</a> <span class="w">feature</span> <span class="q">&#39;:5.10&#39;</span><span class="sc">;</span> <span class="c"># loads all features available in perl 5.10</span></li><li></li><li>    <a class="l_k" href="functions/use.html">use</a> <span class="v">v5.10</span><span class="sc">;</span>           <span class="c"># implicitly loads :5.10 feature bundle</span></li></ol></pre><a name="DESCRIPTION"></a><h1>DESCRIPTION</h1>
<p>It is usually impossible to add new syntax to Perl without breaking
some existing programs.  This pragma provides a way to minimize that
risk. New syntactic constructs, or new semantic meanings to older
constructs, can be enabled by <code class="inline"><a class="l_k" href="functions/use.html">use</a> <span class="w">feature</span> <span class="q">'foo'</span></code>
, and will be parsed
only when the appropriate feature pragma is in scope.  (Nevertheless, the
<code class="inline"><span class="w">CORE::</span></code>
 prefix provides access to all Perl keywords, regardless of this
pragma.)</p>
<a name="Lexical-effect"></a><h2>Lexical effect</h2>
<p>Like other pragmas (<code class="inline"><a class="l_k" href="functions/use.html">use</a> <span class="w">strict</span></code>
, for example), features have a lexical
effect.  <code class="inline"><a class="l_k" href="functions/use.html">use</a> <span class="w">feature</span> <span class="q">qw(foo)</span></code>
 will only make the feature "foo" available
from that point to the end of the enclosing block.</p>
<pre class="verbatim"><ol><li>    <span class="s">{</span></li><li>        <a class="l_k" href="functions/use.html">use</a> <span class="w">feature</span> <span class="q">'say'</span><span class="sc">;</span></li><li>        <a class="l_k" href="functions/say.html">say</a> <span class="q">&quot;say is available here&quot;</span><span class="sc">;</span></li><li>    <span class="s">}</span></li><li>    <a class="l_k" href="functions/print.html">print</a> <span class="q">&quot;But not here.\n&quot;</span><span class="sc">;</span></li></ol></pre><a name="no-feature"></a><h2><code class="inline"><a class="l_k" href="functions/no.html">no</a> <span class="w">feature</span></code>
</h2>
<p>Features can also be turned off by using <code class="inline"><a class="l_k" href="functions/no.html">no</a> <span class="w">feature</span> <span class="q">&quot;foo&quot;</span></code>
.  This too
has lexical effect.</p>
<pre class="verbatim"><ol><li>    <a class="l_k" href="functions/use.html">use</a> <span class="w">feature</span> <span class="q">'say'</span><span class="sc">;</span></li><li>    <a class="l_k" href="functions/say.html">say</a> <span class="q">&quot;say is available here&quot;</span><span class="sc">;</span></li><li>    <span class="s">{</span></li><li>        <a class="l_k" href="functions/no.html">no</a> <span class="w">feature</span> <span class="q">'say'</span><span class="sc">;</span></li><li>        <a class="l_k" href="functions/print.html">print</a> <span class="q">&quot;But not here.\n&quot;</span><span class="sc">;</span></li><li>    <span class="s">}</span></li><li>    <a class="l_k" href="functions/say.html">say</a> <span class="q">&quot;Yet it is here.&quot;</span><span class="sc">;</span></li></ol></pre><p><code class="inline"><a class="l_k" href="functions/no.html">no</a> <span class="w">feature</span></code>
 with no features specified will reset to the default group.  To
disable <i>all</i> features (an unusual request!) use <code class="inline"><a class="l_k" href="functions/no.html">no</a> <span class="w">feature</span> <span class="q">&#39;:all&#39;</span></code>
.</p>
<a name="AVAILABLE-FEATURES"></a><h1>AVAILABLE FEATURES</h1>
<a name="The-'say'-feature"></a><h2>The 'say' feature</h2>
<p><code class="inline"><a class="l_k" href="functions/use.html">use</a> <span class="w">feature</span> <span class="q">'say'</span></code>
 tells the compiler to enable the Perl 6 style
<code class="inline"><a class="l_k" href="functions/say.html">say</a></code> function.</p>
<p>See <a href="functions/say.html">say</a> for details.</p>
<p>This feature is available starting with Perl 5.10.</p>
<a name="The-'state'-feature"></a><h2>The 'state' feature</h2>
<p><code class="inline"><a class="l_k" href="functions/use.html">use</a> <span class="w">feature</span> <span class="q">'state'</span></code>
 tells the compiler to enable <code class="inline"><a class="l_k" href="functions/state.html">state</a></code>
variables.</p>
<p>See <a href="perlsub.html#Persistent-Private-Variables">Persistent Private Variables in perlsub</a> for details.</p>
<p>This feature is available starting with Perl 5.10.</p>
<a name="The-'switch'-feature"></a><h2>The 'switch' feature</h2>
<p><b>WARNING</b>: Because the <a href="perlop.html#Smartmatch-Operator">smartmatch operator</a> is
experimental, Perl will warn when you use this feature, unless you have
explicitly disabled the warning:</p>
<pre class="verbatim"><ol><li>    <a class="l_k" href="functions/no.html">no</a> <span class="w">warnings</span> <span class="q">&quot;experimental::smartmatch&quot;</span><span class="sc">;</span></li></ol></pre><p><code class="inline"><a class="l_k" href="functions/use.html">use</a> <span class="w">feature</span> <span class="q">'switch'</span></code>
 tells the compiler to enable the Perl 6
given/when construct.</p>
<p>See <a href="perlsyn.html#Switch-Statements">Switch Statements in perlsyn</a> for details.</p>
<p>This feature is available starting with Perl 5.10.</p>
<a name="The-'unicode_strings'-feature"></a><h2>The 'unicode_strings' feature</h2>
<p><code class="inline"><a class="l_k" href="functions/use.html">use</a> <span class="w">feature</span> <span class="q">&#39;unicode_strings&#39;</span></code>
 tells the compiler to use Unicode rules
in all string operations executed within its scope (unless they are also
within the scope of either <code class="inline"><a class="l_k" href="functions/use.html">use</a> <span class="w">locale</span></code>
 or <code class="inline"><a class="l_k" href="functions/use.html">use</a> <span class="w">bytes</span></code>
).  The same applies
to all regular expressions compiled within the scope, even if executed outside
it.  It does not change the internal representation of strings, but only how
they are interpreted.</p>
<p><code class="inline"><a class="l_k" href="functions/no.html">no</a> <span class="w">feature</span> <span class="q">&#39;unicode_strings&#39;</span></code>
 tells the compiler to use the traditional
Perl rules wherein the native character set rules is used unless it is
clear to Perl that Unicode is desired.  This can lead to some surprises
when the behavior suddenly changes.  (See
<a href="perlunicode.html#The-%22Unicode-Bug%22">The Unicode Bug in perlunicode</a> for details.)  For this reason, if you are
potentially using Unicode in your program, the
<code class="inline"><a class="l_k" href="functions/use.html">use</a> <span class="w">feature</span> <span class="q">&#39;unicode_strings&#39;</span></code>
 subpragma is <b>strongly</b> recommended.</p>
<p>This feature is available starting with Perl 5.12; was almost fully
implemented in Perl 5.14; and extended in Perl 5.16 to cover <code class="inline"><a class="l_k" href="functions/quotemeta.html">quotemeta</a></code>;
and extended further in Perl 5.26 to cover <a href="perlop.html#Range-Operators">the range operator</a>.</p>
<a name="The-'unicode_eval'-and-'evalbytes'-features"></a><h2>The 'unicode_eval' and 'evalbytes' features</h2>
<p>Together, these two features are intended to replace the legacy string
<code class="inline"><a class="l_k" href="functions/eval.html">eval</a></code> function, which behaves problematically in some instances.  They are
available starting with Perl 5.16, and are enabled by default by a
<code class="inline"><a class="l_k" href="functions/use.html">use</a> <span class="n">5.16</span></code>
 or higher declaration.</p>
<p><code class="inline"><span class="w">unicode_eval</span></code>
 changes the behavior of plain string <code class="inline"><a class="l_k" href="functions/eval.html">eval</a></code> to work more
consistently, especially in the Unicode world.  Certain (mis)behaviors
couldn't be changed without breaking some things that had come to rely on
them, so the feature can be enabled and disabled.  Details are at
<a href="perlfunc.html#Under-the-%22unicode_eval%22-feature">Under the unicode_eval feature in perlfunc</a>.</p>
<p><code class="inline"><a class="l_k" href="functions/evalbytes.html">evalbytes</a></code> is like string <code class="inline"><a class="l_k" href="functions/eval.html">eval</a></code>, but operating on a byte stream that is
not UTF-8 encoded.  Details are at <a href="functions/evalbytes.html">evalbytes EXPR</a>.  Without a
<code class="inline"><a class="l_k" href="functions/use.html">use</a> <span class="w">feature</span> <span class="q">&#39;evalbytes&#39;</span></code>
 nor a <code class="inline"><a class="l_k" href="functions/use.html">use</a> <span class="v">v5.16</span></code>
 (or higher) declaration in
the current scope, you can still access it by instead writing
<code class="inline"><span class="w">CORE::evalbytes</span></code>
.</p>
<a name="The-'current_sub'-feature"></a><h2>The 'current_sub' feature</h2>
<p>This provides the <code class="inline"><a class="l_k" href="functions/__SUB__.html">__SUB__</a></code> token that returns a reference to the current
subroutine or <code class="inline"><a class="l_k" href="functions/undef.html">undef</a></code> outside of a subroutine.</p>
<p>This feature is available starting with Perl 5.16.</p>
<a name="The-'array_base'-feature"></a><h2>The 'array_base' feature</h2>
<p>This feature supports the legacy <code class="inline"><span class="i">$[</span></code>
 variable.  See <a href="perlvar.html#%24%5b">$[ in perlvar</a> and
<a href="arybase.html">arybase</a>.  It is on by default but disabled under <code class="inline"><a class="l_k" href="functions/use.html">use</a> <span class="v">v5.16</span></code>
 (see
<a href="#IMPLICIT-LOADING">IMPLICIT LOADING</a>, below).</p>
<p>This feature is available under this name starting with Perl 5.16.  In
previous versions, it was simply on all the time, and this pragma knew
nothing about it.</p>
<a name="The-'fc'-feature"></a><h2>The 'fc' feature</h2>
<p><code class="inline"><a class="l_k" href="functions/use.html">use</a> <span class="w">feature</span> <span class="q">&#39;fc&#39;</span></code>
 tells the compiler to enable the <code class="inline"><a class="l_k" href="functions/fc.html">fc</a></code> function,
which implements Unicode casefolding.</p>
<p>See <a href="functions/fc.html">fc</a> for details.</p>
<p>This feature is available from Perl 5.16 onwards.</p>
<a name="The-'lexical_subs'-feature"></a><h2>The 'lexical_subs' feature</h2>
<p>In Perl versions prior to 5.26, this feature enabled
declaration of subroutines via <code class="inline"><a name="foo"></a><a class="l_k" href="functions/my.html">my</a> sub <span class="m">foo</span></code>
, <code class="inline"><a name="foo"></a><span class="w">state</span> sub <span class="m">foo</span></code>

and <code class="inline"><a name="foo"></a><a class="l_k" href="functions/our.html">our</a> sub <span class="m">foo</span></code>
 syntax.  See <a href="perlsub.html#Lexical-Subroutines">Lexical Subroutines in perlsub</a> for details.</p>
<p>This feature is available from Perl 5.18 onwards.  From Perl 5.18 to 5.24,
it was classed as experimental, and Perl emitted a warning for its
usage, except when explicitly disabled:</p>
<pre class="verbatim"><ol><li>  <a class="l_k" href="functions/no.html">no</a> <span class="w">warnings</span> <span class="q">&quot;experimental::lexical_subs&quot;</span><span class="sc">;</span></li></ol></pre><p>As of Perl 5.26, use of this feature no longer triggers a warning, though
the <code class="inline"><span class="w">experimental::lexical_subs</span></code>
 warning category still exists (for
compatibility with code that disables it).  In addition, this syntax is
not only no longer experimental, but it is enabled for all Perl code,
regardless of what feature declarations are in scope.</p>
<a name="The-'postderef'-and-'postderef_qq'-features"></a><h2>The 'postderef' and 'postderef_qq' features</h2>
<p>The 'postderef_qq' feature extends the applicability of <a href="perlref.html#Postfix-Dereference-Syntax">postfix dereference syntax</a> so that postfix array
and scalar dereference are available in double-quotish interpolations. For
example, it makes the following two statements equivalent:</p>
<pre class="verbatim"><ol><li>  <a class="l_k" href="functions/my.html">my</a> <span class="i">$s</span> = <span class="q">&quot;[@{ $h-&gt;{a} }]&quot;</span><span class="sc">;</span></li><li>  <a class="l_k" href="functions/my.html">my</a> <span class="i">$s</span> = <span class="q">&quot;[$h-&gt;{a}-&gt;@*]&quot;</span><span class="sc">;</span></li></ol></pre><p>This feature is available from Perl 5.20 onwards. In Perl 5.20 and 5.22, it
was classed as experimental, and Perl emitted a warning for its
usage, except when explicitly disabled:</p>
<pre class="verbatim"><ol><li>  <a class="l_k" href="functions/no.html">no</a> <span class="w">warnings</span> <span class="q">&quot;experimental::postderef&quot;</span><span class="sc">;</span></li></ol></pre><p>As of Perl 5.24, use of this feature no longer triggers a warning, though
the <code class="inline"><span class="w">experimental::postderef</span></code>
 warning category still exists (for
compatibility with code that disables it).</p>
<p>The 'postderef' feature was used in Perl 5.20 and Perl 5.22 to enable
postfix dereference syntax outside double-quotish interpolations. In those
versions, using it triggered the <code class="inline"><span class="w">experimental::postderef</span></code>
 warning in the
same way as the 'postderef_qq' feature did. As of Perl 5.24, this syntax is
not only no longer experimental, but it is enabled for all Perl code,
regardless of what feature declarations are in scope.</p>
<a name="The-'signatures'-feature"></a><h2>The 'signatures' feature</h2>
<p><b>WARNING</b>: This feature is still experimental and the implementation may
change in future versions of Perl.  For this reason, Perl will
warn when you use the feature, unless you have explicitly disabled the
warning:</p>
<pre class="verbatim"><ol><li>    <a class="l_k" href="functions/no.html">no</a> <span class="w">warnings</span> <span class="q">&quot;experimental::signatures&quot;</span><span class="sc">;</span></li></ol></pre><p>This enables unpacking of subroutine arguments into lexical variables
by syntax such as</p>
<pre class="verbatim"><ol><li><a name="foo"></a>    sub <span class="m">foo ($left, $right)</span> <span class="s">{</span></li><li>	<a class="l_k" href="functions/return.html">return</a> <span class="i">$left</span> + <span class="i">$right</span><span class="sc">;</span></li><li>    <span class="s">}</span></li></ol></pre><p>See <a href="perlsub.html#Signatures">Signatures in perlsub</a> for details.</p>
<p>This feature is available from Perl 5.20 onwards.</p>
<a name="The-'refaliasing'-feature"></a><h2>The 'refaliasing' feature</h2>
<p><b>WARNING</b>: This feature is still experimental and the implementation may
change in future versions of Perl.  For this reason, Perl will
warn when you use the feature, unless you have explicitly disabled the
warning:</p>
<pre class="verbatim"><ol><li>    <a class="l_k" href="functions/no.html">no</a> <span class="w">warnings</span> <span class="q">&quot;experimental::refaliasing&quot;</span><span class="sc">;</span></li></ol></pre><p>This enables aliasing via assignment to references:</p>
<pre class="verbatim"><ol><li>    \<span class="i">$a</span> = \<span class="i">$b</span><span class="sc">;</span> <span class="c"># $a and $b now point to the same scalar</span></li><li>    \<span class="i">@a</span> = \<span class="i">@b</span><span class="sc">;</span> <span class="c">#                     to the same array</span></li><li>    \<span class="i">%a</span> = \<span class="i">%b</span><span class="sc">;</span></li><li>    \<span class="i">&amp;a</span> = \<span class="i">&amp;b</span><span class="sc">;</span></li><li>    <a class="l_k" href="functions/foreach.html">foreach</a> \<span class="i">%hash</span> <span class="s">(</span><span class="i">@array_of_hash_refs</span><span class="s">)</span> <span class="s">{</span></li><li>        ...</li><li>    <span class="s">}</span></li></ol></pre><p>See <a href="perlref.html#Assigning-to-References">Assigning to References in perlref</a> for details.</p>
<p>This feature is available from Perl 5.22 onwards.</p>
<a name="The-'bitwise'-feature"></a><h2>The 'bitwise' feature</h2>
<p><b>WARNING</b>: This feature is still experimental and the implementation may
change in future versions of Perl.  For this reason, Perl will
warn when you use the feature, unless you have explicitly disabled the
warning:</p>
<pre class="verbatim"><ol><li>    <a class="l_k" href="functions/no.html">no</a> <span class="w">warnings</span> <span class="q">&quot;experimental::bitwise&quot;</span><span class="sc">;</span></li></ol></pre><p>This makes the four standard bitwise operators (<code class="inline"><span class="i">&amp; |</span> ^ ~</code>
) treat their
operands consistently as numbers, and introduces four new dotted operators
(<code class="inline"><span class="i">&amp;.</span> |. ^. ~.</code>
) that treat their operands consistently as strings.  The
same applies to the assignment variants (<code class="inline">&amp;= |= ^= <span class="i">&amp;.</span>= |.= ^.=</code>
).</p>
<p>See <a href="perlop.html#Bitwise-String-Operators">Bitwise String Operators in perlop</a> for details.</p>
<p>This feature is available from Perl 5.22 onwards.</p>
<a name="The-'declared_refs'-feature"></a><h2>The 'declared_refs' feature</h2>
<p><b>WARNING</b>: This feature is still experimental and the implementation may
change in future versions of Perl.  For this reason, Perl will
warn when you use the feature, unless you have explicitly disabled the
warning:</p>
<pre class="verbatim"><ol><li>    <a class="l_k" href="functions/no.html">no</a> <span class="w">warnings</span> <span class="q">&quot;experimental::declared_refs&quot;</span><span class="sc">;</span></li></ol></pre><p>This allows a reference to a variable to be declared with <code class="inline"><a class="l_k" href="functions/my.html">my</a></code>, <code class="inline"><a class="l_k" href="functions/state.html">state</a></code>,
our <code class="inline"><a class="l_k" href="functions/our.html">our</a></code>, or localized with <code class="inline"><a class="l_k" href="functions/local.html">local</a></code>.  It is intended mainly for use in
conjunction with the "refaliasing" feature.  See <a href="perlref.html#Declaring-a-Reference-to-a-Variable">Declaring a Reference to a Variable in perlref</a> for examples.</p>
<p>This feature is available from Perl 5.26 onwards.</p>
<a name="FEATURE-BUNDLES"></a><h1>FEATURE BUNDLES</h1>
<p>It's possible to load multiple features together, using
a <i>feature bundle</i>.  The name of a feature bundle is prefixed with
a colon, to distinguish it from an actual feature.</p>
<pre class="verbatim"><ol><li>  <a class="l_k" href="functions/use.html">use</a> <span class="w">feature</span> <span class="q">&quot;:5.10&quot;</span><span class="sc">;</span></li></ol></pre><p>The following feature bundles are available:</p>
<pre class="verbatim"><ol><li>  <span class="w">bundle</span>    <span class="w">features</span> <span class="w">included</span></li><li>  --------- -----------------</li><li>  <span class="co">:</span><span class="w">default</span>  <span class="w">array_base</span></li><li></li><li>  <span class="co">:</span><span class="n">5.10</span>     <a class="l_k" href="functions/say.html">say</a> <span class="i">state</span> switch <span class="w">array_base</span></li><li></li><li>  <span class="co">:</span><span class="n">5.12</span>     <a class="l_k" href="functions/say.html">say</a> <span class="i">state</span> switch <span class="w">unicode_strings</span> <span class="w">array_base</span></li><li></li><li>  <span class="co">:</span><span class="n">5.14</span>     <a class="l_k" href="functions/say.html">say</a> <span class="i">state</span> switch <span class="w">unicode_strings</span> <span class="w">array_base</span></li><li></li><li>  <span class="co">:</span><span class="n">5.16</span>     <a class="l_k" href="functions/say.html">say</a> <span class="i">state</span> switch <span class="w">unicode_strings</span></li><li>            <span class="w">unicode_eval</span> <span class="w">evalbytes</span> <span class="w">current_sub</span> <span class="w">fc</span></li><li></li><li>  <span class="co">:</span><span class="n">5.18</span>     <a class="l_k" href="functions/say.html">say</a> <span class="i">state</span> switch <span class="w">unicode_strings</span></li><li>            <span class="w">unicode_eval</span> <span class="w">evalbytes</span> <span class="w">current_sub</span> <span class="w">fc</span></li><li></li><li>  <span class="co">:</span><span class="n">5.20</span>     <a class="l_k" href="functions/say.html">say</a> <span class="i">state</span> switch <span class="w">unicode_strings</span></li><li>            <span class="w">unicode_eval</span> <span class="w">evalbytes</span> <span class="w">current_sub</span> <span class="w">fc</span></li><li></li><li>  <span class="co">:</span><span class="n">5.22</span>     <a class="l_k" href="functions/say.html">say</a> <span class="i">state</span> switch <span class="w">unicode_strings</span></li><li>            <span class="w">unicode_eval</span> <span class="w">evalbytes</span> <span class="w">current_sub</span> <span class="w">fc</span></li><li></li><li>  <span class="co">:</span><span class="n">5.24</span>     <a class="l_k" href="functions/say.html">say</a> <span class="i">state</span> switch <span class="w">unicode_strings</span></li><li>            <span class="w">unicode_eval</span> <span class="w">evalbytes</span> <span class="w">current_sub</span> <span class="w">fc</span></li><li>            <span class="w">postderef_qq</span></li><li></li><li>  <span class="co">:</span><span class="n">5.26</span>     <a class="l_k" href="functions/say.html">say</a> <span class="i">state</span> switch <span class="w">unicode_strings</span></li><li>            <span class="w">unicode_eval</span> <span class="w">evalbytes</span> <span class="w">current_sub</span> <span class="w">fc</span></li><li>            <span class="w">postderef_qq</span></li></ol></pre><p>The <code class="inline"><span class="j">:</span><span class="w">default</span></code>
 bundle represents the feature set that is enabled before
any <code class="inline"><a class="l_k" href="functions/use.html">use</a> <span class="w">feature</span></code>
 or <code class="inline"><a class="l_k" href="functions/no.html">no</a> <span class="w">feature</span></code>
 declaration.</p>
<p>Specifying sub-versions such as the <code class="inline"><span class="n">0</span></code>
 in <code class="inline"><span class="v">5.14.0</span></code>
 in feature bundles has
no effect.  Feature bundles are guaranteed to be the same for all sub-versions.</p>
<pre class="verbatim"><ol><li>  <a class="l_k" href="functions/use.html">use</a> <span class="w">feature</span> <span class="q">&quot;:5.14.0&quot;</span><span class="sc">;</span>    <span class="c"># same as &quot;:5.14&quot;</span></li><li>  <a class="l_k" href="functions/use.html">use</a> <span class="w">feature</span> <span class="q">&quot;:5.14.1&quot;</span><span class="sc">;</span>    <span class="c"># same as &quot;:5.14&quot;</span></li></ol></pre><a name="IMPLICIT-LOADING"></a><h1>IMPLICIT LOADING</h1>
<p>Instead of loading feature bundles by name, it is easier to let Perl do
implicit loading of a feature bundle for you.</p>
<p>There are two ways to load the <code class="inline"><span class="w">feature</span></code>
 pragma implicitly:</p>
<ul>
<li>
<p>By using the <code class="inline">-<span class="w">E</span></code>
 switch on the Perl command-line instead of <code class="inline">-e</code>
.
That will enable the feature bundle for that version of Perl in the
main compilation unit (that is, the one-liner that follows <code class="inline">-<span class="w">E</span></code>
).</p>
</li>
<li>
<p>By explicitly requiring a minimum Perl version number for your program, with
the <code class="inline"><a class="l_k" href="functions/use.html">use</a> <span class="w">VERSION</span></code>
 construct.  That is,</p>
<pre class="verbatim"><ol><li>    <a class="l_k" href="functions/use.html">use</a> <span class="v">v5.10.0</span><span class="sc">;</span></li></ol></pre><p>will do an implicit</p>
<pre class="verbatim"><ol><li>    <a class="l_k" href="functions/no.html">no</a> <span class="w">feature</span> <span class="q">&#39;:all&#39;</span><span class="sc">;</span></li><li>    <a class="l_k" href="functions/use.html">use</a> <span class="w">feature</span> <span class="q">&#39;:5.10&#39;</span><span class="sc">;</span></li></ol></pre><p>and so on.  Note how the trailing sub-version
is automatically stripped from the
version.</p>
<p>But to avoid portability warnings (see <a href="functions/use.html">use</a>), you may prefer:</p>
<pre class="verbatim"><ol><li>    <a class="l_k" href="functions/use.html">use</a> <span class="n">5.010</span><span class="sc">;</span></li></ol></pre><p>with the same effect.</p>
<p>If the required version is older than Perl 5.10, the ":default" feature
bundle is automatically loaded instead.</p>
</li>
</ul>




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