elisp and rewrite url for firefox

[Hugh Lawson]

What are the functions in elisp that do the below?

change from                   to
-----------             ----------------
ftp.debian.org          ftp://debian.org
www.debian.org          http://www.debian.org

'browse-url-at-point' makes this happen, but the elisp code is too
advanced for me to follow.  I made up my own homemade function to do
this, but I'd like to know if I can just send a string to an already
existing elisp function that would do it for me.  Here's my code:

;; variable url is already set, so it adds "http://"; etc
;; as necessary

   (cond ((string-match "http://\\|https://\\|ftp://"; url 0) url)
          ((string-match "ftp\\." url 0) (setq url (concat "ftp://"url)) )
          (t(setq url (concat "http://"; url))))

To make firefox open an url in a new tab I must send it the full url.

Here is the whole function, which seems to work OK.
 
(defun my-browser (url &optional new-window)
  "Open URL in a new tab in firefox. To use this, set
   browse-url-browser-function to my-browser"
  (interactive (browse-url-interactive-arg "URL: "))
  (cond ((string-match "http://\\|https://\\|ftp://"; url 0) url)
        ((string-match "ftp\\." url 0) (setq url (concat "ftp://"url)) )
        (t(setq url (concat "http://"; url))))
;; 
;; remainder adapted from Xning Lee code
;; see
;; http://lists.gnu.org/archive/html/info-gnus-english/2004-07/msg00193.html
;;
  (when
      (string-match ".*No running window found.*" 
                    (shell-command-to-string 
                     (concat "firefox -remote 'openurl(" url ",new-tab)'")))
    (message "Starting Firefox...")
    (start-process (concat "firefox " url) nil
                   "/bin/sh" "-c" (concat "firefox " url "|| true"))
    (message "Starting Firefox...done")))

;; to make make my-browser default, add the below.
(setq browse-url-browser-function 'my-browser)

-- 
Hugh Lawson
hlawson@triad.rr.com