Help with External HTTP Monitor (cURL) - Requires http authentication

Hello, we use the code as external monitor when checking the websites with NTLM authentication. It works well, when the webpage return a response where we can match the return string (in the response payload). However, when we need to check for the response code (e.g. 200 OK), the monitor will fail to match and will mark the pool member DOWN. Is there a way how we could match for the HTTP responses/status codes with this or similar script? In our case, we are looking for existence od a .dll file on the server.