use vars qw($ssh_channel);
use Net::SSH2;
...
my $ssh = Net::SSH2->new();
$ssh->connect('host') or die "!Connect: $@";
$ssh->auth_password('user','password') or die "!Auth: $@";
my $ssh_channel = $ssh->channel();
$ssh_channel->blocking(0);
$ssh_channel->shell();
...
my $ver = &sshcmd('show version');
print "Version: $ver\n";
...
sub sshcmd
{
        my $cmd = shift;
        my $extra = shift;
        my ($data, $buf, $len) = ('', '', 0);
        $ssh_channel->write($cmd."\r");
        $ssh_channel->flush();
        select(undef,undef,undef,0.2);
        while ($len = $ssh_channel->read($buf, 512))
        {
                $data .= $buf;
        }
        my @res = split("\r\n", $data);
        shift @res;
        pop @res;
        return (wantarray ? @res : join("",@res) ) unless ($extra);
        return $res[0] if ($extra eq 'first');
        return $res[$#res] if ($extra eq 'last');
}