Perl 5 vs 6 (or Go, Python, Ruby et al); which language(s) FTW, and why?

Several of the solutions use a library function to do the main parsing. It makes sense if one is available. And it may be more robust if the library code is well written.

I'm a Perl fan. I love Perl 6. Imo, if you partition the Perl 6 solution into (what will clearly become) library functions (the grammar bit) and actual code (the "for @cases" bit), it's shorter and more readable than most of the other solutions.