Ack. So somewhere in epl-loop, we're trying to treat 't as a sequence, but the condition-case in perl-interpreter-new is hiding where. If you can remove the condition-case and try again, you might get something more informative. Alternatively, you can instrument epl-loop by going to it and typing \C-u \C-\M-x, then step through to see where the bogosity occurs. Unfortunately, the function's sort of large, so I can't see where the error is :(.