Upon reading the title, this is one of those "I know that's possible, but I'd never bother to implement it" things, although this particular implementation isn't exactly what I had in mind.
The technical write up is worth perusing but I played a game before reading and accidentally found a winning strategy immediately. I'm not sure if this is a result of the 2-ply nature of the engine or if the mentioned deficiencies account for this but the computer did not act to prevent checkmate in 1 (without any intervening check); the game I played was (in algebraic notation):
1. e4 e5
2. kf3 kf6
3. kxe5 kxe4
4. d4 kxf2
5. Kxf2 a5
6. Qf3 b5??
7. Qxf7
1-0
It’s turing complete so you could compile almost any language to regex. You might have to build a vm for some languages, also in regex. The point is, it’s regex all the way down.
During my CS years I remember being fascinated by NFA's, as opposed to boring single universe DFA's.
For some reason I internalized that I would never see something like an NFA implemented beyond text books.
Then came Carlini.