;;; Nice would be something like
;;; (split-when (= % :x) [1 2 3 4 :x 5 6 7 8 :x 9 10 :x 11] ==>
;;; ((1 2 3 4) (:x) (5 6 7 8) (:x) (9 10) (:x) (11))
;;;
;;; How to do this easier than:

(use 'clojure.contrib.seq-utils)

(let [group (atom 1), old (atom true)]
  (group-by #(if (= % :x)
	       (do
		 (reset! old false)
		 (swap! group inc))
	       (if @old
		 @group
		 (do
		   (reset! old true)
		   (swap! group inc))))
	    [1 2 3 4 :x 5 6 7 8 :x 9 10 :x 11]))

;;; ?
;;; While this is not exactly the same result as above
;;; but the data format comes close.