The Starlark language might be of interest

I think RESL and Skylark follow pretty similar goals.
https://github.com/bazelbuild/starlark?tab=readme-ov-file#tour

Skylark is essentially a subset of Python that can be used for complex build/configuration files/macros. It's fast and deterministic. It has variables, functions methods etc. But it's safe to execute and cannot access FS, network, time etc (no access to the standard library).