title: Comparison of Regex flavours
body: <p>I wonder if there is a comparison between the features of various regex metacharacters in various implementations.</p>
  
  <p>The sort of thing I am looking for is a table like </p>
  
  <pre><code>Language       Perl    sed
  grouping       ( )     \( \)
  </code></pre>
  
  <p>Languages I am interested in are Perl, Sed Java  Javascript</p>