Have you looked at the Lisps / Scheme / Racket yet? Racket in particular makes it quite nice to go #lang blah at the top of the file and change the parsing or interpretation entirely.

For example all the documentation pages and guides are written in scribble:

https://docs.racket-lang.org/scribble/getting-started.html#(part._first-example)

#lang scribble/base
 
@title{On the Cookie-Eating Habits of Mice}
 
If you give a mouse a cookie, he's going to ask for a
glass of milk.

And it has an entire document markup language created in it, which can output pdf or html. But you can still use @ syntax to drop in racket code to compute values. Or create templates.

I even implemented a #lang which took assembly directly (and interpreted it, it was for a class).

So if you are really after full control, you should study Lisps and their macro systems.

Careful you don’t come off as a sealion.

Though this is a thread about Wayland so eh.

Thanks, you made me feel old today. Get off my lawn.

I’ve watched some slow typists program, and I think I have the answer. If it takes you a while to type the code out, you are much more likely to stick to the first approach that works, and not rewrite it as much.