That's not true. You only have to prepend #' if you pass the function by value (as in your web server handler example).

If you call the function by name yourself, like (foo arg), and you recompile foo, any code that called foo will see the new version.

Hmm, I’ll try it again, but I remember issues with the function call syntax too. Iirc, it had to do with the fact that redefinitions don’t count if the use site is running in another thread. But I’ll double-check this when I get a chance.