What's up with character classes not working?
I guess I'll have to live with doing [0-9] instead of \d, but why must I do [A-Fa-f0-9] instead of [:xdigit:]? I thought POSIX regular expressions included this feature!
Sigh... Has anyone found a definitive documentation on allowed regex syntax for this problem? I hate using the online judge as a tester - 256 submissions might not be that many after all.