The predicates of this section form a tightly related set for realising premature successfull or failing exits from a block . These predicates are first of all useful for error-recovery. They were primarily implemented for compatibily reasons. Execute Goal in a block .
Label is the name of the block.
Label is normally an atom, but the system imposes no type constraints and may even be a variable. The block's ExitValue is unified with Value . If this unification fails the block fails. Cut all choice-points created since the entry of the innermost block which Label unifies.