[onetwo12]

Prolog is only appropriate for certain kinds of programs, long time ago I programmed in prolog and it was a very difficult task when the problem was not about matching and unification.

For me Lisp was much more appropiate and easy to program. Forward chaining and unification is not enough for certain class of algorithms, sometime you need backward chaining, probabilistic inference and many other ideas that are not easily translated in prolog. I remember some discussion about the semantic of clauses. For example misil(ready), is this about the misil is already ready, or that you are going to prepare the misil, etc. I find that concurrency and paralelism in prolog are not easy. In the book "on Lisp" by P. Grahan there is a prolog interpreter in Lisp, this can be interesting for somebody wishing to learn prolog.

Edit,Added, erlang was inspired by prolog, so learning prolog will help you learn erlang, but if you are a ruby type elixir is your best option.