title: A regular expression to match a Perl expression?
body: <p>Trying to mangle Perl source code (trying to implement a macro), I wonder (I doubt it) whether there exists a <em>Perl regular expression</em> to <strong>match one Perl expression</strong> (or <em>one function parameter</em>, if you prefer that view of things).
  The expression may be arbitrary complex, even using multiple lines.</p>
  
  <p>AFAIK things like "balanced parentheses" are impossible to do with pure regular expressions. Unfortunately all the source filters (like <code>Filter::Simple</code>) seem to be based on regular expressions.</p>