c's case fall-through

2.14: adda/cstr/c's case fall-through:
. if the case src is a set the case should do
multiple things (concurrently?) .
. to provide c's case fall-through,
it should use the (enter [/]case).stmt .
. will case labels conflict?
the users know what literals they're casing,
and they can choose goto labels that don't conflict;
but what about nested cases?
to jump from one case stmt to an enclosing one,
use a goto label
or use ../case ?