elisp -ruby change block from do to {

ruby-change-block.el

(defun ruby-change-block() 
  (interactive)
  (save-excursion
    (let (beg end start-char end-char start-line end-line block-content one-liner)
      (ruby-beginning-of-block)

      (progn 
        (re-search-forward "do")
        (backward-kill-word 1);; kill "do"
        (setq beg (point)
              start-char "{" 
              end-char " }"
              one-liner t)
        (ruby-end-of-block)
        (setq end (point))
        (kill-word 1);; kill 'end'
        (setq start-line (line-number-at-pos beg)
              end-line (line-number-at-pos end)
              number-of-lines (- end-line start-line)
              block-content (buffer-substring-no-properties beg end))
        (kill-region beg end )

        ;; remove tabs
        (setq block-content (replace-regexp-in-string "^ *" " " 
                                                            block-content))

        (insert (concat start-char block-content end-char))      
        (if (and one-liner (= number-of-lines 2 )  );;1 line of code
            ;; move to one line
            (progn 
              (ruby-end-of-block)
              (setq end (+ 1 (point)))
              (ruby-beginning-of-block)
              (beginning-of-line 1)
              (while (< (point) end  )
                (end-of-line 1)
                (kill-forward-chars 1)
                )))))))