Currently `trap` has no way to set a signal to the system default. Rather `trap - PIPE` for example sets the signal handling to the value it have upon entrance to the shell. It's common enough for systems to disable SIGPIPE, so it would be useful to support a shell wrapper that would renable standard SIGPIPE handling.
I'm not sure what syntax to use for this, maybe: `trap + PIPE` Note we've recently added the --default-signal=PIPE option to env(1) to support this functionality, though it would be useful and symmetrical to have this supported by the shell also. thanks, Pádraig.
