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<html><head><title>Hash::Util (Perl in a Nutshell, 2nd Edition)</title><link rel="stylesheet" type="text/css" href="../style/style1.css" /><meta name="DC.Creator" content="Stephen Spainhour" /><meta name="DC.Format" content="text/xml" scheme="MIME" /><meta name="DC.Language" content="en-US" /><meta name="DC.Publisher" content="O'Reilly & Associates, Inc." /><meta name="DC.Source" scheme="ISBN" content="0596002416L" /><meta name="DC.Subject.Keyword" content="stuff" /><meta name="DC.Title" content="Perl in a Nutshell, 2nd Edition" /><meta name="DC.Type" content="Text.Monograph" /></head><body bgcolor="#ffffff"><img src="gifs/smbanner.gif" usemap="#banner-map" border="0" alt="Book Home" /><map name="banner-map"><area shape="rect" coords="1,-2,616,66" href="index.htm" alt="Java and XSLT" /><area shape="rect" coords="629,-11,726,25" href="jobjects/fsearch.htm" alt="Search this book" /></map><div class="navbar"><table width="684" border="0"><tr><td align="left" valign="top" width="228"><a href="ch08_118.htm"><img src="../gifs/txtpreva.gif" alt="Previous" border="0" /></a></td><td align="center" valign="top" width="228" /><td align="right" valign="top" width="228"><a href="ch08_120.htm"><img src="../gifs/txtnexta.gif" alt="Next" border="0" /></a></td></tr></table></div><h2 class="sect1">8.119. Hash::Util</h2><p><a name="INDEX-1467" />Offers aselection of general-utility hash subroutines. Starting with Perl5.8, hashes allow you to restrict access to the datathat's stored in the hash. Individual keys can belocked so they cannot be deleted, nor can their values be changed.Hash::Util is largely intended to replace the deprecatedpseudo-hashes.</p><p>For example:</p><blockquote><pre class="code"> #!/usr/local/bin/perl -w%hash = (foo => 42, bar => 23);lock_keys(%hash);# Now, try to set %hash{'something'}while(my($key, $value) = each %hash) { print "$key -> $value\n";}unlock_keys(%hash);</pre></blockquote><p> You can lock specific values as follows:</p><blockquote><pre class="code">#!/usr/local/bin/perl -w%hash = (foo => 42, bar => 23);lock_key(%hash, 'foo');# Now, try to set 'foo' and see what happensunlock_keys(%hash, 'foo');</pre></blockquote><hr width="684" align="left" /><div class="navbar"><table width="684" border="0"><tr><td align="left" valign="top" width="228"><a href="ch08_118.htm"><img src="../gifs/txtpreva.gif" alt="Previous" border="0" /></a></td><td align="center" valign="top" width="228"><a href="index.htm"><img src="../gifs/txthome.gif" alt="Home" border="0" /></a></td><td align="right" valign="top" width="228"><a href="ch08_120.htm"><img src="../gifs/txtnexta.gif" alt="Next" border="0" /></a></td></tr><tr><td align="left" valign="top" width="228">8.118. Getopt::Std</td><td align="center" valign="top" width="228"><a href="index/index.htm"><img src="../gifs/index.gif" alt="Book Index" border="0" /></a></td><td align="right" valign="top" width="228">8.120. I18N::Collate</td></tr></table></div><hr width="684" align="left" /><img src="../gifs/navbar.gif" usemap="#library-map" border="0" alt="Library Navigation Links" /><p><p><font size="-1"><a href="copyrght.htm">Copyright © 2002</a> O'Reilly & Associates. All rights reserved.</font></p><map name="library-map"><area shape="rect" coords="1,0,85,94" href="../index.htm"><area shape="rect" coords="86,1,178,103" href="../lwp/index.htm"><area shape="rect" coords="180,0,265,103" href="../lperl/index.htm"><area shape="rect" coords="267,0,353,105" href="../perlnut/index.htm"><area shape="rect" coords="354,1,446,115" href="../prog/index.htm"><area shape="rect" coords="448,0,526,132" href="../tk/index.htm"><area shape="rect" coords="528,1,615,119" href="../cookbook/index.htm"><area shape="rect" coords="617,0,690,135" href="../pxml/index.htm"></map></body></html>⌨️ 快捷键说明
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