Re: file-name-shadow-mode

[Richard Stallman]

    Cute.  It makes the assumption, however, that there is a unique point
    where that equivalence occurs.  I don't think that this is correct:
    whenever you split in the middle of an environment variable name,
    you'll get a nonmatch that can turn into a match if you happen to look
    further.

What about doing a linear scan from the end?  It might be too
slow...but it might be perfectly fast enough.  It is sufficient
to test places where there is a /, ~, or $.  There usually
won't be many of them.