mingw/html/lib/Symbol.html

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  13 <big><strong><span class="block">&nbsp;Symbol - manipulate Perl symbols and their names</span></strong></big>
  14 </td></tr>
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  16
  17 <p><a name="__index__"></a></p>
  18 <!-- INDEX BEGIN -->
  19
  20 <ul>
  21
  22         <li><a href="#name">NAME</a></li>
  23         <li><a href="#synopsis">SYNOPSIS</a></li>
  24         <li><a href="#description">DESCRIPTION</a></li>
  25         <li><a href="#bugs">BUGS</a></li>
  26 </ul>
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  29 <hr />
  30 <p>
  31 </p>
  32 <h1><a name="name">NAME</a></h1>
  33 <p>Symbol - manipulate Perl symbols and their names</p>
  34 <p>
  35 </p>
  36 <hr />
  37 <h1><a name="synopsis">SYNOPSIS</a></h1>
  38 <pre>
  39     use Symbol;</pre>
  40 <pre>
  41     $sym = gensym;
  42     open($sym, &quot;filename&quot;);
  43     $_ = &lt;$sym&gt;;
  44     # etc.</pre>
  45 <pre>
  46     ungensym $sym;      # no effect</pre>
  47 <pre>
  48     # replace *FOO{IO} handle but not $FOO, %FOO, etc.
  49     *FOO = geniosym;</pre>
  50 <pre>
  51     print qualify(&quot;x&quot;), &quot;\n&quot;;              # &quot;Test::x&quot;
  52     print qualify(&quot;x&quot;, &quot;FOO&quot;), &quot;\n&quot;        # &quot;FOO::x&quot;
  53     print qualify(&quot;BAR::x&quot;), &quot;\n&quot;;         # &quot;BAR::x&quot;
  54     print qualify(&quot;BAR::x&quot;, &quot;FOO&quot;), &quot;\n&quot;;  # &quot;BAR::x&quot;
  55     print qualify(&quot;STDOUT&quot;, &quot;FOO&quot;), &quot;\n&quot;;  # &quot;main::STDOUT&quot; (global)
  56     print qualify(\*x), &quot;\n&quot;;              # returns \*x
  57     print qualify(\*x, &quot;FOO&quot;), &quot;\n&quot;;       # returns \*x</pre>
  58 <pre>
  59     use strict refs;
  60     print { qualify_to_ref $fh } &quot;foo!\n&quot;;
  61     $ref = qualify_to_ref $name, $pkg;</pre>
  62 <pre>
  63     use Symbol qw(delete_package);
  64     delete_package('Foo::Bar');
  65     print &quot;deleted\n&quot; unless exists $Foo::{'Bar::'};</pre>
  66 <p>
  67 </p>
  68 <hr />
  69 <h1><a name="description">DESCRIPTION</a></h1>
  70 <p><code>Symbol::gensym</code> creates an anonymous glob and returns a reference
  71 to it.  Such a glob reference can be used as a file or directory
  72 handle.</p>
  73 <p>For backward compatibility with older implementations that didn't
  74 support anonymous globs, <code>Symbol::ungensym</code> is also provided.
  75 But it doesn't do anything.</p>
  76 <p><code>Symbol::geniosym</code> creates an anonymous IO handle.  This can be
  77 assigned into an existing glob without affecting the non-IO portions
  78 of the glob.</p>
  79 <p><code>Symbol::qualify</code> turns unqualified symbol names into qualified
  80 variable names (e.g. ``myvar'' -&gt; ``MyPackage::myvar'').  If it is given a
  81 second parameter, <code>qualify</code> uses it as the default package;
  82 otherwise, it uses the package of its caller.  Regardless, global
  83 variable names (e.g. ``STDOUT'', ``ENV'', ``SIG'') are always qualified with
  84 ``main::''.</p>
  85 <p>Qualification applies only to symbol names (strings).  References are
  86 left unchanged under the assumption that they are glob references,
  87 which are qualified by their nature.</p>
  88 <p><code>Symbol::qualify_to_ref</code> is just like <code>Symbol::qualify</code> except that it
  89 returns a glob ref rather than a symbol name, so you can use the result
  90 even if <code>use strict 'refs'</code> is in effect.</p>
  91 <p><code>Symbol::delete_package</code> wipes out a whole package namespace.  Note
  92 this routine is not exported by default--you may want to import it
  93 explicitly.</p>
  94 <p>
  95 </p>
  96 <hr />
  97 <h1><a name="bugs">BUGS</a></h1>
  98 <p><code>Symbol::delete_package</code> is a bit too powerful. It undefines every symbol that
  99 lives in the specified package. Since perl, for performance reasons, does not
 100 perform a symbol table lookup each time a function is called or a global
 101 variable is accessed, some code that has already been loaded and that makes use
 102 of symbols in package <code>Foo</code> may stop working after you delete <code>Foo</code>, even if
 103 you reload the <code>Foo</code> module afterwards.</p>
 104 <table border="0" width="100%" cellspacing="0" cellpadding="3">
 105 <tr><td class="block" style="background-color: #cccccc" valign="middle">
 106 <big><strong><span class="block">&nbsp;Symbol - manipulate Perl symbols and their names</span></strong></big>
 107 </td></tr>
 108 </table>
 109
 110 </body>
 111
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