I guess you have to call the pty method on the $chan to get a pseudo tty allocated on the remote side.

Also, as it seems that you are on a Unix/Linux system, you may like to use Net::OpenSSH instead of Net::SSH2:

my $ssh = Net::OpenSSH->new($host, user => $user, password => $passwor
+d);
$ssh->error and die "SSH connection failed: " . $ssh->error;

$ssh->system({tty => 1}, $ARGV[0])
    or die "remote command failed: ". $ssh->error;
[download]