On: Mangle, a programming language for deductive database programming

[throwaway484]

I can think of a few others…

Sawzall, a language focused around processing logs. Rob Pike led on this but use has pretty much all been replaced by Go. https://en.m.wikipedia.org/wiki/Sawzall_(programming_languag...

Dex, a language focused around array processing from the team behind the Jax machine learning library. Early stage research project. https://github.com/google-research/dex-lang

Rune, a language focused on security, early stage research project. https://github.com/google/rune

Wuffs, a language focused on writing safe file format handlers (parsing, encoding, decoding) https://github.com/google/wuffs

[d3nj4l → throwaway484]

Cue and skylark (now starlark), too.

[fidgewidge → throwaway484]

Also other internal languages: borgmon, borgcfg. Don't think they use borgmon anymore though.