$sftp = Net::SFTP::Foreign->new($host);
$sftp->error and die "unable to connect to remote host: " . $sftp->error;

##</code><code>##

my %args = ( host     => "localhost",
         user     => "user",
         port     => "22",
         # psw    => "psw",
         key_path => "/home/user/.ssh/id_rsa" );

my $sftp = Net::SFTP::Foreign->new(%args);
$sftp->die_on_error("Unable to establish SFTP connection");