negative lookbehind only works with a fixed string. You cannot have variable-width negative lookbehind.
The immediate solution is to reverse your regex, converting a negative lookbehind into a positive lookahead. Regex::Reverse tricky test cases and sexeger are probably good starts on the process.
- In general, if you think something isn't in Perl, try it out, because it usually is. :-)
- "What is the sound of Perl? Is it not the sound of a wall that people have stopped banging their heads against?"