Speaking of regex and ruby...

I came across this link: http://macromates.com/textmate/manual/regular_expressions

This is a nice summary (with link to original source document) of the regex library used in ruby. Related the UTF-8 regex issues I commented on, the document describes what subset \w actually matches with u extension. It may be out of date (not sure), but it is the most thorough documentation of the ruby regex I have stumbled across.