Convert spaces to tabs in Emacs

spaces2tabs4.el

(defun four-spaces-to-tab (&optional begin end)
  "Replace four spaces with a tab in a region."
  (interactive "r")
  (save-excursion
	  (if mark-active 
		  (replace-regexp "    " "\t" nil (point) (mark))
		(replace-regexp "    " "\t" nil (point-min) (point-max))
		)		
	  )
  )

spaces2tabs8.el

(defun eight-spaces-to-tab (&optional begin end)
  "Replace eight spaces with a tab in a region."
  (interactive "r")
  (save-excursion
	  (if mark-active 
		  (replace-regexp "        " "\t" nil (point) (mark))
		(replace-regexp "        " "\t" nil (point-min) (point-max))
		)		
	  )
  )