BTW, this is how you read from both stderr and stdout:

use Net::OpenSSH;

my $ssh = Net::OpenSSH->new($host, ...);
$ssh->error and die "connection failed: " . $ssh->error;

my (undef, $ofh, $efh, $pid) = $ssh->open_ex({ stdout_pipe => 1,
                                               stderr_pipe => 1 },
                                             @cmd)
    or die "ssh command failed: " . $ssh->error;

while(1) {
  # select loop to read from $ofh and $efh without blocking
  # ...
}

waitpid($pid, 0); 
print "result: $?\n";
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