Regex pattern for Alpha Numeric values

@ithcy: POSIX character classes are rather passé in that they tend to work only with the nasty, old-style 8-bit locales. They don’t make much sense in a Unicode world, at least not without extensions. It depends on whether they’re compliant with UTS#18.

Actually, \w in a Perl regex does not mean an alphanumunder, contrary to popular misunderstanding. Rather, it means exactly [\p{Alphabetic}\p{Decimal_Number}\p{Mark}\p{Connector_Punctuation}]. Close, but not equivalent.

@tchrist: Which characters except for alphanumeric and underscore match \w?

@Tim: I just told you: Marks, Connector Punctuation. Also, Alphabetic includes Other_Alphabetic; it is certainly not just Letters. Also, \w is only Decimal Numbers and Letter Numbers; there are other numeric types it does not match. You should get unichars to play around with this. You’ll likely also want uniprops and perhaps uninames, too.

@tchrist: You are right. Looks like perlre made the same mistake: "A '\w' matches a single alphanumeric character (an alphabetic character, or a decimal digit) or '_'"