old_contents: var http = require('helma/httpserver');
  http.start({
      port: 8080,
      moduleName: 'jack/narwhal',
      functionName: 'Narwhal'
  });
  
  // Alternatively, you can pass the jack app to start() as second argument.
  // this bypasses module loading in the servlet, so changes in the Jack app won't be picked up.
  // http.start({ port: 8080 }, require('jack/narwhal').Narwhal);
  
new_contents: try {
  
      // fail fast if no jack libs on the module path
      require('jack/narwhal');
  
      var http = require('helma/httpserver');
      http.start({
          port: 8080,
          moduleName: 'jack/narwhal',
          functionName: 'Narwhal'
      });
  
      // Alternatively, you can pass the jack app to start() as second argument.
      // this bypasses module loading in the servlet, so changes in the Jack app won't be picked up.
      // http.start({ port: 8080 }, require('jack/narwhal').Narwhal);
  
  } catch (error) {
      print();
      print("Can't start Jack demo. Make sure you have Jack installed and configured as described in README.txt.");
      print();
      print(error);
  }
  
subject: Print message and exit if jack libs can't be loaded.