Change response in Fiddler

FiddlerScript.cs

static function OnBeforeRequest(oSession: Session) {
  if (oSession.RequestMethod == 'GET' && oSession.PathAndQuery.IndexOf('part_of_your_url') > 0) {
    oSession.utilCreateResponseAndBypassServer();
    oSession.oResponse.headers.HTTPResponseCode = 401;
    oSession.oResponse.headers.HTTPResponseStatus = '401 Not Authorized';
    oSession.oResponse.headers['Access-Control-Allow-Origin'] = '*';
    oSession.utilSetResponseBody('response_body');
  }
}