How to put a value in my success ajax function parameter from my controller in ruby on rails

I have a following ajax request in my java script and it is calling run_me method in my controller.

 $.ajax({
    type: 'GET',
    url:'/static_pages/run_me',
    data: {my_name: envi},
    success: function(){
      $('#loadingmessage').hide();
      $('#show_ip').show();
    }
  });

Now I want to put a value from my method in the controller ( just a random (local) value not a instance variable) and pass it to the parameter in the success : function.

success: function(var){}

I saw lots of thread in stackoverflow and they were talking about use respond_to method but I didnt really understand them! Can some one explain this to me Thanks