Check if they mean FTP over SSL or SFTP. SFTP is the SSH file transfer protocol. It is not FTP over SSH; it is a completely different protocol. Net::SFTP implements SFTP.
They may mean FTP with TLS/SSL. The draft that describes this is http://www.ietf.org/internet-drafts/draft-murray-auth-ftp-ssl-11.txt
As far as I know, Net::FTP does not support TLS, and there is no module doing TLS as an FTP client.