I have heard rumours that Perl 5 is not parseable by any kind of earthly grammar. However, I'm wondering if one could get close, and if anyone has actually tried.

Perltidy?

• Sourceforge
• cpan

And then, there's cperl, the perl syntax highlighting mode for Emacs. Funny how the first matches Google comes up with, are in the hates-software domain, so I guess it's not all swell. :) Nothing to do with how it parses perl, however.