Too easy, I can do that. Only a couple of open questions, but if you don't have the answers I think I know what would work best anyway:

* Sub-regexps, non-matching groups, lookaheads - this PR disables them, but I'm on the fence on if this is a good thing, it definitely helps with consistency though since named non-matching and lookaheads are just broken and nested groups may entail the expectation of nested named params too
* Periods in regexps - I'm going to allow them to be used as regexp characters inside the group since there is no way to "unescape" them but a user can always escape them trivially

Thoughts?