my $ssh_gw = Net::OpenSSH->new($gw); # no password given, authenticate
                                     # using public key on the gateway

my $proxy_command = $ssh_gw->make_remote_command('nc %h %p');

my $ssh = Net::OpenSSH->new($host,
                            password => $password, # request password authentication
                            master_opts => [-o => "ProxyCommand=$proxy_command"]);