Interesting. Back in the day there were some pretty good BASIC implementations that were still quite small. The whole of the MOS and BASIC on the BBC micro ran in 16+16K. That should be portable to the Arduino, but it has only a little bit of RAM. With $2 more you have a RPi Pico which would be a massive step up in terms of hardware (ok, one AD channel less), clock speed and RAM size. You could probably run a fairly large high level language in there.