Regex support

[ThatsNoMoon]

Consider using a capture group for positive matches, if the group isn't captured then the match is ignored.

My main concern with this is ensuring that users can't exploit it easily. A lot of care will have to be taken, and limitations should be put on e.g. the length of allowed regexes. Regexes will have to be cached (if regex doesn't do that already) to avoid repetitive compilation costs. Ideally some benchmarks on how fast the current text-based matching is can be compared to regex-based matching, including with very complicated regexes.