Exec that remembers in which group it was invoked

A simple addition to exec command that remembers the group it was invoked in.
For example if I invoke exec-here in web group for firefox and change my group to term it would still exec the firefox in the web group and not the current active group. This could just plainly replace the old exec function as I think this is what people expect from exec function.
XMonad-contrib contains similar function.