use Net::SFTP::Foreign 1.67;
use Net::SFTP::Foreign::Backend::Net_SSH2 0.04;

my $sftp = Net::SFTP::Foreign->new( host => 'delivery.myserver.com',
                                    port => '22',
                                    backend => 'Net_SSH2',
                                    user => 'ftp_user',
                                    key_path => "mytransaction.private.key");
$sftp->die_on_error("Unable to establish SFTP connection");