expression evaluator (with variables and optional REPL) in MiniScript
The first version (eval_v1) was coded in about 40 minutes during a Twitch live stream on Feb. 21, 2022.
I later came back and made a new version (eval.ms), based on Pratt parsing. See the blog post explaining how it works.
If you've just come here looking for an expression evaluator for use in your MiniScript project, eval.ms is all you need.