I would rephrase this to learn a new programming paradigm. There are fundamental differences between static typing and dynamic typing, object orientation and functional, manual memory management and garbage collection. There are also "pure" single-paradigm languages and multi-paradigm languages. If you learn the same type of language multiple times, you're really just learning new syntax and probably a couple of extra idiosyncrasies, so it's important that you pick languages with fundamental differences.
I would rephrase this to learn a new programming paradigm. There are fundamental differences between static typing and dynamic typing, object orientation and functional, manual memory management and garbage collection. There are also "pure" single-paradigm languages and multi-paradigm languages. If you learn the same type of language multiple times, you're really just learning new syntax and probably a couple of extra idiosyncrasies, so it's important that you pick languages with fundamental differences.
Compare going through this learning path:
Perl -> PHP -> JavaScript -> Python -> Ruby -> Node.js
To going through this:
Java -> C -> Scheme -> JavaScript -> Erlang
For example.