Hash Rocketを1.9記法に置換するelisp

Rubyの古いHash記法 { :foo => 'bar' } を1.9以降の記法 { foo: 'bar' } に置換するelispです。

(defun ruby-anti-hash-rocket ()
  (interactive)
  (beginning-of-line)
  (setq current-line (count-lines (point-min) (point)))
  (setq replaced (replace-regexp-in-string ":\\([a-z0-9_]+\\)\s*=>" "\\1:" (buffer-string)))
  (erase-buffer)
  (insert replaced)
  (goto-line (+ 1 current-line))
  (beginning-of-line)
  )