;; an example, if the value is 'buffer-file-name then all buffers
;; who are visiting files are suitable, but others (like dired
;; buffers) are not;
-;; * a list -- then if the buufer is suitable iff its mode is in the
-;; list, exccept if the first element is nil in which case the test
+;; * a list -- then the buffer is suitable iff its mode is in the
+;; list, except if the first element is `not', in which case the test
;; is reversed (i.e. it is a list of unsuitable modes).
;; * Otherwise, the buffer is suitable if its name does not begin with
;; ` ' or `*' and if `buffer-file-name' returns true.