"Toggle word checking on or off...
function! WordCheck ()
   "Toggle the flag (or set it if it doesn't yet exist)...
   let w:check_words = exists('w:check_words') ? !w:check_words : 1

   "Turn match mechanism on/off, according to new state of flag...
   if w:check_words
      exec s:words_matcher
   else
      match none
   endif
endfunction