No I think they are related but different. For instance with pdb or the clojure repl I"ll add entire new functions or classes and try them out.

With gdb or jdb that might be theoretically possible but it certainly is not convenient or commonly done. Typically your stretching things with a complicated one liner expression.

But you are right concepts are pretty close, its just that I find a lot of things that call themselves "debuggers" don't have the ability to add new code. Things that call themselves "repls" dont' have the ability to stop at a point or context like a debugger. pdb being the exception. Why can't we have tools that do both things well.

Ah, I forgot to mention gdb as well. gdb and python hooked me on this way of developing.