1> (define hair-colors 
      (pair-up '(ib per ann) '("black" "green" "pink")))

2> hair-colors
((ib . "black") (per . "green") (ann . "pink"))

3> (find-in-list (lambda (ass) (eq? (car ass) 'per)) hair-colors)
(per . "green")

4> (find-in-list (lambda (ass) (equal? (cdr ass) "pink"))
                  hair-colors)
(ann . "pink")

5> (find-in-list (lambda (ass) (equal? (cdr ass) "yellow"))
                  hair-colors)
#f

6> (let ((pink-person
          (find-in-list
            (lambda (ass) (equal? (cdr ass) "pink")) hair-colors)))
    (if pink-person (car pink-person) #f))
ann