That's an incorrect way of writing the following:

use lib "/home/geoffleach/src/lib";
use My::Example;
[download]

The OP claimed this doesn't work. Your version won't work any better. (It's in fact worse since it doesn't include the related arch dir.)

(Also, it doesn't make much sense to hardcode absolute paths to library directories. Use PERL5LIB for absolute paths, and use use lib for relative paths.)