Thanks for proofreading that. I installed the attached to try to fix the 
problems you noted.

I also fixed a couple of other problems if I happened to run across them. First, 
the regexp [a-b-c] is ambiguous according to POSIX, and should be avoided. 
Second, a regexp like [[:alnum:]-z] is also ambiguous for the same reason. 
Perhaps these regexps currently have a particular behavior in Emacs but it's not 
documented as far as I know and code should avoid them. Perhaps the trawler 
could be modified to catch them.