> I suggest looking at Forth implementations, which is where I think most interpreter innovation has happened.

Fortunately the Forth community write about their techniques, so you don't have to just eyeball gforth's source-code. A handful of links for those interested:

https://www.complang.tuwien.ac.at/papers/

https://github.com/ForthPapersMirror/Papers

https://www.complang.tuwien.ac.at/projects/forth.html

https://www.complang.tuwien.ac.at/anton/euroforth/

http://soton.mpeforth.com/flag/jfar/vol7.html

http://soton.mpeforth.com/flag/fd/

http://www.forth.org/literature.html

http://www.forth.org/fd/contents.html