The thing that surprised me was that you can't write an interpreter in an interpreted language, at least not in obsd. It is possible if you jump through a few hoops but you can't directly call it.

An example: if you made a language in python /bin/my_lang: #does nothing but pretend it does

    #!/usr/local/bin/python3
    import sys
    print('my_lang args', sys.argv)
    for line in sys.stdin:
      print('invalid_line:', line)

my_script:

    #!/bin/my_lang
    line of stuff
    another line of stuff

    chmod u+x my_script
    ./my_script

Probably for the best, but I was a bit sad that my recursive interpreter scheme was not going to work.

Update: looks like linux does allow nested interpreters, good for them.

https://www.in-ulm.de/~mascheck/various/shebang/#interpreter...

really that whole document is a delightful read.