I want to be able to route embedded calls to the debugger
if a switch is set, but return the result to the caller,
so it can continue.  I can do it now, by:
- to run a string expression 'str':
	if debugging
	    pdb.run("_res = <str>")
	    res = getattr(main, "_res")
	else
	    res = run_string(<str>,...)
- to run a func(*args):
	predefine a dummy function:
	    def runit(func, args):
	        global _res
	        _res = apply(func, args)
	if debugging
	    pdb.runcall(dummy.runit, func, args)
	    res = getattr(dummy, "_res")
	else
	    res = call_object(func, args)
but this seems a roundabout way of doing it.  Is there an 
easy way to do this (subclassing Pdb,...)?
Mark L.