_submit and _validate get the form in a ordinate way... but they don't output anything on screen.
Suppose I want to do something as stupid as multiplying 2 fields and return the output on screen without having to save the 2 fields somewhere... as if _submit was not going to return a path but just use $form_values in spite of $_POST and output something...
I gave a look at how search works and at a quick glance it looks not suited. Up to my understanding it parse keys and then _submit append it to a url.
thanks