I wrote this custom language. It's on Github, but the example code that would have been available would be very limited.
I gave it two inputs -- the original bash script and an example of my pipeline language (unrelated jobs).
The code it gave me was syntactically correct, and was really close to the final version. I didn't have to edit very much to get the code exactly where I wanted it.
This is to say -- if a novel language is somewhat similar to an existing syntax, the LLM will be surprisingly good at writing it.