Tons of language are secret weapons if you use it for what they were created. Here are some more outside of Erlang, that I know of and I'm sure there's more.

Tons of language are secret weapons if you use it for what they were created. Here are some more outside of Erlang, that I know of and I'm sure there's more. APL/J/K - mathematical algorithms Prolog - logic, tons of business rules Forth/Lisp - bottom up programming, when you have an idea of the primitives you need to tackle a problem, but not exactly sure how to put it together. Assembly - When you must absolutely run impossibly fast especially on very small CPUs AWK/Perl - slice and dice text files For these languages, I don't substitute for any language. I'll never slice and dice with Java, Python, Go. I don't care. Awk or Perl. I'll never implement tons of rules in any other language, I don't care what logic library they implement without first doing so in Prolog. For the solo programmer, the above languages hold very true. I have played around with Erlang since Prolog influenced it's syntax, but I'm yet to have to build a large scale fault tolerant system that needs it, but the knowledge is tucked away at the back of my memory should I ever. I feel that Python, Javascript and Go can also be some sort of secret weapon if used in the right place.