function to pack folders

[Mark Moll <mmoll@cs.cmu.edu>]

I wrote this little function to renumber articles in my nnml folders. I
don't know that much about elisp, but this seemed a reasonable way to do it.
For some reason, however, I get the following error when I call the function 
below in the summary buffer.

      Symbol's value as variable is void: group

It's probably something very trivial, but can anybody tell me what I'm
doing wrong?

(defun mm-pack-folder ()
  "Renumber the articles such that holes in the numbering are removed."
  (interactive)
  (let ((group gnus-newsgroup-name)
	(folder (replace-in-string
		 (replace-in-string group 
				    "\\(nnml\\+archive:\\)\\(.*\\)"
				    "archive/\\2")
		 "\\(nnml:\\)\\(.*\\)" "\\2"))
	(dir (concat message-directory folder)))
    (call-process "gunzip" nil nil nil (concat dir "/*.gz"))
    (call-process "folder" nil nil nil (concat "+" folder) "-pack")
    (nnml-generate-nov-databases-1 (concat dir))
    (call-process "gzip" nil nil nil (concat dir "/*"))
    (gnus-summary-reselect-current-group)))

-- 
Mark Moll