You find the real error message in your web server error log. Look at that and remedy the cause.

Also, I really suggest you rewrite this script. It is horribly insecure and allows for arbitrary remote code execution:

$node = param("node");
...
$sysinfo = `sudo -u rsnagios ssh $node bin/sysinfo|sed s/-/_/`;
[download]

$node is not sanitized or checked against a list of valid hostnames. If you call your script with node="wget http://perlmonks.org" it will run the wget executable. As a first fix, you should only allow hostnames that match \w+ in $node.