title: Use Perl regex attributes in awk
body: <p>I like to use the Perl regex engines in the GNU <code>grep</code>: </p>
  
  <pre><code>$ echo FOO | grep -P '(?i)foo'
  FOO
  </code></pre>
  
  <p>I use it many times with good results. </p>
  
  <p>Sometimes I use <code>awk</code> because I think it has better regex handling than bash shell - but the regex in <code>awk</code> are not the same as Perl. </p>
  
  <p>I use <code>awk</code>, <code>gawk</code> and I find different regex modifiers for the <code>awk</code>. 
  In travels I find 3 different regex modifiers for <code>awk</code>/<code>gawk</code> </p>
  
  <pre><code>--posix
  --traditional
  --re-interval
  </code></pre>
  
  <p>Do you know if there is species of <code>awk</code> that use the Perl regex like the <code>grep</code> examples above?</p>