X

If  X  is  instantiated  to  a  term which would be acceptable as body of a
clause,  the  goal X is executed exactly as if that term appeared textually
in  place  of  the  X.   In  particular,  any  cut  ('!') occurring in X is
interpreted as if it occurred in the body of the clause containing X.  If X
is not instantiated as described the clause fails.