OCaml is more of a multi-paradigm language than Haskell. It's not purely functional, so you can easily fallback into imperative code if you need (you can use mutable variables, I/O, mutable arrays, hashmaps, for loops, while loops, etc.). It's also object-oriented (though this feature is not widely used) and has a very powerful module system that few other languages can compare to.

What I like about it from a learning perspective is that it makes a transition into functional programming much simpler than it would be with Haskell, where you have to completely change the way you program from the very beginning.