lexical scope and dynamic extent

[mips!escargot.earl@glacier (Earl Killian)]

Some entities in the language are described as having lexical scope
and dynamic extent, which means that they can be refered to after
they're gone.  Do any of the implementations have good ways of
detecting such things?  Here's a nasty one:

(defun foo ()
  (tagbody
    l (return-from foo #'(lambda () (go l)))))
(funcall (foo))

If you type this at various implementations, what do you get?