Alice began to get rather sleepy, and went on saying to herself, in a dreamy sort of way "Do cats eat bats? Do cats eat bats?" and sometimes "Do bats eat cats?", for, you see, as she couldn't answer either question, it didn't much matter which way she put it.'
By it not having meaning, Alice is able to play with the order of the words solely for sonic pleasure. Drawing attention to playfulness of language.
For the reader, these obviously don't mean the same thing. Showing that Alice is not in control of the meaning the language it evokes - 'autonomous language'.