Using a module that's not installed in the normal places Perl looks always takes an extra step:

use lib '/your/module/directory';
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After you do that, Perl will look in that directory for any subsequent modules you load. You still have to load Net::FTP:

use Net::FTP;   # after the earlier use statement
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So you need both those steps (point Perl at the right place, then load the module). You can't compress it into one, as you're trying to do.