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POperl non-greedy problem
 

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  1. POperl non-greedy problem
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    <p>I am having a problem with a non-greedy regular expression. I've seen that there are questions regarding non-greedy regex, but they don't answer to my problem.</p> <p><strong>Problem:</strong> I am trying to match the href of the "lol" anchor. </p> <p><strong>Note:</strong> I know this can be done with perl HTML parsing modules, and my question is <strong>not</strong> about parsing HTML in perl. My question is about the regular expression itself and the HTML is just an example.</p> <p><strong>Test case:</strong> I have 4 tests for <code>.*?</code> and <code>[^"]</code>. The 2 first produce the expected result. However the 3rd doesn't and the 4th just does but I don't understand why.</p> <p><strong>Questions:</strong> </p> <ol> <li><strong>Why</strong> does the 3rd test fail in both tests for <code>.*?</code> and <code>[^"]</code> ? Shouldn't the non-greedy operator work?</li> <li><strong>Why</strong> does the 4th test works in both tests for <code>.*?</code> and <code>[^"]</code> ? I don't understand why including a <code>.*</code> in front changes the regex. (the 3rd and 4th tests are the same except the <code>.*</code> in front).</li> </ol> <p>I probably don't understand exactly how these regex work. A <a href="http://docstore.mik.ua/orelly/perl/cookbook/ch06_16.htm" rel="nofollow">perl cookbook recipe</a> mentions something but I don't think it answers my question.</p> <pre><code>use strict; my $content=&lt;&lt;EOF; &lt;a href="/hoh/hoh/hoh/hoh/hoh" class="hoh"&gt;hoh&lt;/a&gt; &lt;a href="/foo/foo/foo/foo/foo" class="foo"&gt;foo &lt;/a&gt; &lt;a href="/bar/bar/bar/bar/bar" class="bar"&gt;bar&lt;/a&gt; &lt;a href="/lol/lol/lol/lol/lol" class="lol"&gt;lol&lt;/a&gt; &lt;a href="/koo/koo/koo/koo/koo" class="koo"&gt;koo&lt;/a&gt; EOF print "| $1 | \n\nThat's ok\n" if $content =~ m~href="(.*?)"~s ; print "\n---------------------------------------------------\n"; print "| $1 | \n\nThat's ok\n" if $content =~ m~href="(.*?)".*&gt;lol~s ; print "\n---------------------------------------------------\n"; print "| $1 | \n\nWhy does not the 2nd non-greedy '?' work?\n" if $content =~ m~href="(.*?)".*?&gt;lol~s ; print "\n---------------------------------------------------\n"; print "| $1 | \n\nIt now works if I put the '.*' in the front?\n" if $content =~ m~.*href="(.*?)".*?&gt;lol~s ; print "\n###################################################\n"; print "Let's try now with [^]"; print "\n###################################################\n\n"; print "| $1 | \n\nThat's ok\n" if $content =~ m~href="([^"]+?)"~s ; print "\n---------------------------------------------------\n"; print "| $1 | \n\nThat's ok.\n" if $content =~ m~href="([^"]+?)".*&gt;lol~s ; print "\n---------------------------------------------------\n"; print "| $1 | \n\nThe 2nd greedy still doesn't work?\n" if $content =~ m~href="([^"]+?)".*?&gt;lol~s ; print "\n---------------------------------------------------\n"; print "| $1 | \n\nNow with the '.*' in front it does.\n" if $content =~ m~.*href="([^"]+?)".*?&gt;lol~s ; </code></pre>
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    1. COYou state a problem and say that there is a solution that produces an expected result. I'm not sure what the question is.
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    2. COYou are right, I wasn't precise enough. I edited and stated the question more clearly.
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