> I want to restructure stuff, make multiple versions of functions, move them in and out of comment blocks or just leave code there for REPL use.

I think programming at the REPL requires a very different mindset from how a lot of us learned initially. The thought of leaving commented code in our codebase is one of those things we're told not to do, but there's a great snippet from one of Stuart Halloway's talks where he mentions "Rich Comments" (pun intended I think).

Rich is apparently known for leaving REPL code inside comment blocks specifically for testing purposes, and as a sort of transcript of the work that was done. [0]

Its a great approach, and one that I've adopted, but it seems wrong at first glance when taken out of the context of a REPL.

[0] https://github.com/clojure/clojure/blame/4ef4b1ed7a2e8bb0aaa...