Re: The craziest RegExes you ever created

[Ovid]

My craziest regex:

  use re 'eval';
  my $string = "abc";
  my $length = length $string;
  my $regex
    = qr/(\G[$string]{0,$length}(?{print "# [$&][$'][$string]\n"}))/ x
+ 2;
  $string =~ $regex;

Bonus points if you can figure out why I wrote that. As a fun exercise, try to figure out what it does and how it does it.

Of course, this forking regular expression might top it. Since the regex engine is not re-entrant, if you need that power, you have to fork.