The main issue is that Perl is case sensitive and that the module is actually File::Find. On a case insensitive file system you get weird results such as this because the module file gets found despite the error in the file name case, but the package isn't found.

Note that you need $File::Find::dir to access the dir variable too. This should have been caught with warnings - you'd have gotten:

Name "File::File::dir" used only once: possible typo at noname.pl line
+ 12.
[download]

when you ran the script.