(LETREC PERM
  (PERM LAMBDA (L)
    (IF (EQ L (QUOTE NIL)) (QUOTE NIL)
        (INSERT (CAR L) (PERM (CDR L)))))
  (INSERT LAMBDA (X A)
    (IF (EQ A (QUOTE NIL)) (CONS X (QUOTE NIL))
        (OR (CONS X A) (CONS (CAR A) (INSERT X (CDR A)))))))&