do-until

code.clj

(defmacro do-until [& clauses]
  (when clauses
    (list
     `when (first clauses)
     (if (next clauses)
       (second clauses)
       (throw (IllegalArgumentException.
               "do-until requires an even number of forms")))
     (cons 'do-until (nnext clauses)))))

usage.clj

(do-until 
  true (println "Line 1") 
  nil (println "Line 2")
  true (println "Line 3"))

; => "Line 1"