(defmacro ->
      "Threads the expr through the forms. Inserts x as the
      second item in the first form, making a list of it if it is not a
      list already. If there are more forms, inserts the first form as the
      second item in second form, etc."
      {:added "1.0"}
      [x & forms]
      (loop [x x, forms forms]
        (if forms
          (let [form (first forms)
                threaded (if (seq? form)
                           (with-meta `(~(first form) ~x ~@(next form)) (meta form))
                           (list form x))]
            (recur threaded (next forms)))
          x)))