use strict;
use Net::SSH::Perl;

my $ssh = Net::SSH::Perl->new('localhost',debug => 1, protocol => '2,1');
$ssh->login('username','password');
my ($stdout, $stderr, $exit) = $ssh->cmd('cat /tmp/a 1>&2');
print $stdout . "\n";
print $stderr . "\n";
print $exit . "\n";