The problem is that the Lib::File module apparently does not support the export the tag ':filetest'.

I could not find the module on CPAN, but google found this:
http://www.lackas.net/imp/docs/Lib/File.html

Unfortunately I don't see the code listed, so I cannot check what the module exports. You can though. Find this file (Lib/File.pm) and look through the source to see whether it uses the Exporter module to control what tokens it exports. If so, look for %EXPORT_TAGS.

You should also search for 'sub import', which would be custom import behaviour.

Perhaps you meant to do this: use filetest;
The filetest module is listed as "Perl pragma to control the filetest permission operators".
Read perldoc filetest for more information.