It sounds like you're already aware of this from your question and others have already beat me to the punch, but: OCaml modules are best of breed. Better than

It sounds like you're already aware of this from your question and others have already beat me to the punch, but: OCaml modules are best of breed. Better than anything else. Nothing else even comes close. They're weird and different from modules you'll see in other languages. Then after you get used to them you'll find those other modules are at best neutered and most likely severely broken versions of what you've come to know and love from OCaml (or any of the true MLs). OCaml modules arise from a certain treatment of "existential types" which are, in a lot of ways, the very foundation of type abstraction. If you don't care about types practically, then you can care about them spiritually as a means of describing program interfaces. Existential types are maybe the very foundation of abstract program interfaces. So, OCaml is at least 50% good. Opam is kind of nice, too.