Exercise 4.53: With permanent-set! as
described in Exercise 4.51 and if-fail as in Exercise 4.52,
what will be the result of evaluating


(let ((pairs '()))
  (if-fail 
   (let ((p (prime-sum-pair 
             '(1 3 5 8) 
             '(20 35 110))))
     (permanent-set! pairs 
                     (cons p pairs))
     (amb))
   pairs))