title: Combine 'if' and 'if not' in perl
body: <p>I have got the following filter inside my <code>httpd.conf</code>:</p>
  <pre><code>ExtFilterDefine jsonfilter mode=output intype=application/json cmd=&quot;/usr/bin/perl -pe 's|^|qq(\,\&quot;) . valid . qq(\&quot;\: ) . qq(\&quot;) . time() . \\x0D . qq(\&quot;) . qq(\\n)|e if ($==eof) &amp;&amp;  unless (-f q{/tmp/md5_filter.tmp})'&quot;
  </code></pre>
  <p>But the way how I used the <code>&amp;&amp;</code> operater is not valid. I receive no output if I request the file. The filter should only run if the <code>md5_filter.tmp</code> file doesn't exists and <code>s</code> command should only add the timestamp at the <code>end of file (eof)</code>. Does somebody know what's wrong with my code?</p>