Examples:

• q(X), which is defined in the following, is equivalent to p(X), except all interruptions are ignored.

        q(X):-catch(p(X),interrupt,q(X)).
  

• The query catch(p(X),undefined_predicate(_),fail) fails p(X) if an undefined predicate is called during its execution.
• The query catch(q,C,write(hello_q)), where q is defined in the following, succeeds with the unifier C=c and the message hello_q.

        q :- r(c).
        r(X) :- throw(X).
  

• The query catch(p(X),E,p(X)==E) for the following program fails, because E is unified with a renamed copy of p(X), rather than p(X) itself.

         p(X):-throw(p(X)).