Rails on OCaml (2019-03-19) : « ML-based functional programming may be "the next big thing" in programming languages. »
OCaml inherits from the long line of Meta-Languages (1970) object-functional and statically typed. It can be interpreted, bytecoded or natively compiled, with official french academic (INRIA) tools, packaged in Debian format.
Some ressources to learn OCaml :