@(do
   (defmacro while ((condition : result) . body)
     (let ((cblk (gensym "cnt-blk-"))
           (bblk (gensym "brk-blk-")))
       '(macrolet ((break (value) '(return-from ,',bblk ,value)))
          (symacrolet ((break (return-from ,bblk))
                       (continue (return-from ,cblk)))
            (block ,bblk
              (for () (,condition ,result) ()
                (block ,cblk ,*body)))))))

   (let ((i 0))
     (while ((< i 100))
       (if (< (inc i) 20)
         continue)
       (if (> i 30)
         break)
       (prinl i)))

   (prinl
     (sys:expand
       '(while ((< i 100))
          (if (< (inc i) 20)
            continue)
          (if (> i 30)
            break)
          (prinl i)))))