So why not just learn Common Lisp first? Coming from a procedural and OOP background, my experience has been that I didn’t really understand functional programming until I had to use it exclusively. Once functional programming is comfortable, you can add the rest of the tools that Common Lisp makes available, and use whatever tool is best at the task at hand. Larry Coleman on Stack Exchange

When I write LISP to configure Emacs, I don’t know whether it’s better to use functional idioms (the few of which I know) or procedural ones. Seeing how pure functional programming works thus seems like a good idea. I’ll try (again) to learn Haskell before I try to get more serious about LISP than my current abilities to wrench my Emacs configuration into shape.