Although others have already helped out, thought I'd toss out another method. You can use DamianConway's Regexp::Debugger module to step through the matching process. For a video demo, you can watch his video presentation from YAPC::NA 2012 at http://youtu.be/zcSFIUiMgAs. (Note: At the time of the video recording, the module had not yet been released to CPAN.)