in reply to
[Win32] Verify filename (case sensitively)
Just yesterday, I investigated that in relation to generating a warning on Windows when a module is loaded with the "wrong" case, like use Strict;. I found this (C++) post, which seems to be fairly OK. It does not do an extra stat() call per file, but a call to SHGetFileInfoW. I don't know if that's horribly slow or not.
The linked subroutine tries to verify all parts of the path, while at least Perl would only be interested in the last part(s) of the name.