;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; set the machine-name variable and function
(defvar machine-name (system-name) "Machine name for this system.")
(defun machine-name ()
  "Return the name of the machine you are running on, as a string.
Same as (system-name) up to the first '.'"
  (concat machine-name))
(let
  ((i 1) (s (system-name)) (sl (length (system-name))))
  (while (< i sl)
    (if
        (string-equal "." (substring s i (1+ i)))
        (setq i (length s))  ;; bail out
        (progn ;; keep looping
          (setq machine-name (substring s 0 (setq i (1+ i))))
          )
        )
    )
)

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; rewrite mode-line (A B C ... Y Z) as (A B C .. Y foo bar baz Z)
(let ((revx (reverse default-mode-line-format)))
  (setq default-mode-line-format
        (reverse (append
                  ;; Things to insert penultimately:
                  (reverse (list
                            (concat
                             "--"
                             (user-login-name)
                             "@"
                             machine-name  ;; or use (system-name) if you like
                             )
                            (car revx)
                            ))
                  (cdr revx)))))
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;