I think obviously it's much _easier_ to create a mess in Clojure this way, but I think in most sane codebases the pure and impure stuff is quite neatly demarcat

I think obviously it's much _easier_ to create a mess in Clojure this way, but I think in most sane codebases the pure and impure stuff is quite neatly demarcated. Generally people have learned to structure systems as some sort of root data structure containing various components, which can be started, stopped or reset at will. You have to put that in place yourself, but I've not worked on a project where it's been an issue in many years. For what it's worth, I have found dynamically loading new libraries at runtime easier in Clojure than Haskell, which is another source of REPL friction for me, although I rarely use the latter these days.