(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)))