(defmacro loop-do-chunked (chunk-sym list n &body body)
  (let ((elt-sym (gensym "elt"))
        (i-sym (gensym "i"))
        (n-sym (gensym "n")))
    `(loop
        with ,chunk-sym = nil
        with ,n-sym = ,n
        for ,elt-sym in ,list
        for ,i-sym from 1
        do (push ,elt-sym ,chunk-sym)
        when (zerop (mod ,i-sym ,n-sym)) do
          (progn (progn ,@body)
                 (setf ,chunk-sym nil))
        finally (when ,chunk-sym
                  (progn ,@body)))))