Ещё один вариант итерации по хэш-таблице

(with-hash-table-iterator (my-iterator *my-hash*)
    (loop
      (multiple-value-bind (entry-p key value)
          (my-iterator)
        (if entry-p
            (print-hash-entry key value)
            (return)))))
; The value associated with the key FIRST-KEY is ONE
; The value associated with the key SECOND-KEY is TWO
; The value associated with the key THIRD-KEY is NIL
; The value associated with the key NIL is NIL-VALUE
; NIL