I am referring to what comes after the word match, i.e.
match = '[_]([^\_ ]|\.| .[^\])*[_]'; match = '^[^\t].*((.|-|?|:|;|,)\s*)'; or match = '//\s*.*$';
Those are regular expressions; a means to match bits of text:
http://en.wikipedia.org/wiki/Regular_Expressions
Taking your last match there for instance, it would match a forward slash (/) twice, any amount of whitespace (\s*), then any characters or spaces at all (.*) until the end of the line ($).
As for the specific grammar TextMate uses:
http://www.macromates.com/textmate/manual/regular_expressions