(with-monad %state-monad
             (let* ((been-there? #f)
                    (number (mbegin %state-monad
                              (return 1)
                              (begin
                                (set! been-there? #t)
                                (return 2))
                              (return 3))))
               (pk 'before been-there?) (run-with-state number %state-monad) (pk 'after been-there?)))

;;; (before #f)

;;; (after #t)