A breakloop is a REPL operating in the context of condition handling. When a condition is signaled, you can use the breakloop to modify state and direct how the condition should be handled (including fixing something local and letting the current function proceed by ignoring the condition).
Seems like that would only be doable by altering CPython to at least have a hook in the initial exception processing (or maybe there is some magic double-underscore thing for that already?).
I see. That's pretty similar to the feature set of [pdb](https://docs.python.org/3/library/pdb.html). You may then logically ask "Does Hy support pdb?". The answer is "sort of". I've fixed one or two bugs, but we don't test it. I suspect there are various features of pdb that assume Python syntax and would need some hooks to get working properly with Hy.
Seems like that would only be doable by altering CPython to at least have a hook in the initial exception processing (or maybe there is some magic double-underscore thing for that already?).