It's psudo-recursion. You can't call an alias from within itself, and until recently mIRC wouldn't let you call an alias that already existed in the call stack. However, now that you can recall an alias that already exists in the callstack, you can do something like this:

ALIAS Recursion $$1-

If you want to call an alias recursively, it'd look somewhat like:
ALIAS dostuff { somestuff $1 | recursion dostuff $2- }

Another problem is mIRC only permits a callstack of 100 items (or was it 200 now?)

- Raccoon