This module lets you defer actions at run-time that will take place when
the control flow returns into an upper scope.  Currently, you can:

* hook an upper scope end with "reap" ;

* localize variables, array/hash values or deletions of elements in
higher contexts with respectively "localize", "localize_elem" and
"localize_delete" ;

* return values immediately to an upper level with "unwind", and know
which context was in use then with "want_at".