I'm not sure what "the regex consortium" (if that existed) has to say about this, but why limit this to unicode *alpha*. What Why not unicode numbers? What's wrong with `日万` (Sun-10_000) as an identifier (vs `日10_000`)?. For that matter, I think an identifier could start with a non-ascii number (`万日`). In any case, D syntax allows such a name.

Also, I think it will also choke on `_`? I think that should definitely be accepted.