Recommend me a scripting language

I've been looking around for a scripting language that:

• has a cli interpreter
• is a "general purpose" language (yes, awk is touring complete but no way I'm using that except for manipulating text)
• allows to write in a functional style (ie. it has functions like map, fold, etc and allows to pass functions around as arguments)
• has a small disk footprint
• has decent documentation (doesn't need to be great: I can figure out most things, but I don't want to have to look at the interpter source code to do so)
• has a simple/straightforward setup (ideally, it should be a single executable that I can just copy to a remote system, use to run a script and then delete)

Do you know of something that would fit the bill?

Here's a use case (the one I run into today, but this is a recurring thing for me).

For my homelab I need (well, want) to generate a luhn mod n check digit (it's for my provisioning scripts to generate synchting device ids from their certificates).

I couldn't find ready-made utilities for this and I might actually need might a variation of the "official" algorithm (IIUC syncthing had a bug in their initial implementation and decided to run with it).

I don't have python (or even bash) available in all my systems, and so my goto language for script is usually sh (yes, posix sh), which in all honestly is quite frustrating for manipulating data.