I've fallen out of like with exercism, but I'm curious what your reason was? I still recommend it for people wanting to sample a new language but I found the exercises in all the tracks were a bit too generic and didn't appropriately demonstrate the unique aspects of each language. Particularly with languages like Erlang and Elixir, they had few exercises which really demonstrated concurrency and message passing as baked-in language facilities. (I pulled it back up, I only found two exercises that promoted using concurrency for Erlang.)