->_.clj

(use 'clojure.walk)

(defmacro ->_
  "Threads the forms, replacing underscores with the result of the last expression."
  ([x] x)
  ([x form] (if (seq? form)
              (with-meta (postwalk-replace {'_ x} form) (meta form))
              (list form x)))
  ([x form & more] `(->_ (->_ ~x ~form) ~@more)))

(comment

(macroexpand-all '(->_ 5 (+ 7 _) (* _ 9) (- _ 88)))
;; (- (* (+ 7 5) 9) 88)

(->_ [1 2 3] last (* _ _))
(->_ 5 (partial + _) (comp inc _ _) (_ 10))

)