The easiest way to retrieve statistics or configuration information from network devices is to use SNMP.

In any case, using Net::SSH2 correctly is quite hard and often involves looking at the module source code or even at libssh2 one. If you are on a Unix/Linux box, Net::OpenSSH is far easier to use.

You can even perform the querying in parallel using Net::OpenSSH::Parallel:

use Net::OpenSSH::Parallel;

my $pssh = Net::OpenSSH::Parallel;

$pssh->add_host($_, user => $user, password => $password) for @hosts;
$pssh->all(parsub => \&query_device);
$pssh->run;

sub query_device {
    my ($host, $ssh) = @_;
    my $output = $ssh->capture({ stdin_data => <<EOD, stderr_to_stdout
+ => 1 });
enable
$secret
term len 0;
sh mls cef sum
EOD
    $output =~ s/\s+/ /g;
    print "data from $host: $output\n";
}
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