rosie VS langs

I think you'd be better served to try to port Rosie Pattern Language (https://gitlab.com/rosie-pattern-language/rosie) to Kotlin than to try to roll your own. There are definite corner cases in RegEx (sounds like you've already hit some) where the asympototic performance is so large that the code is practically unrunnable. Rosie addresses several of those cases.

I had to spend a lot of time clicking through links to finally find an example: https://gitlab.com/rosie-pattern-language/rosie/blob/master/rpl/date.rpl

Something could be based on the "Rosie Pattern Language"[0]. There is already a parser for en_US/en_EU dates[1], which should be simple to extend to date ranges.

[0]: https://gitlab.com/rosie-pattern-language/rosie/-/blob/maste...

[1]: https://gitlab.com/rosie-pattern-language/rosie/blob/master/...

Maybe something like Rosie?

Well, I only wrote a few dozen lines in each. (Those benchmarks I wrote are here, all in one file; scroll through to find them. Those two will be at the end.

Next I tried writing a custom C program just for the VM execute function; mostly this was a framework machine-generated from my interpreter, with the handlers necessary filled in manually.

This is my doswitch/u-based test program, a mini-interpreter executing a loop.

Actually the next thing I did after trying svm.c was to port it to my systems language to see how my compiler managed with it. (Source is here.)

I have taken something away from Forth which is the (a--b) notation that describes the stack behaviour. I use it in these early docs of my IL here.