How can invalidate the authenticity token for a signup form after the first POST request is received in rails applications?

Question

My application will create a batch of new accounts on a Pitchfork attack. My application provides a authenticity token when the signup form is viewed. I want to invalidate this token once the first PUT request containing this token arrives, so that no other user accounts can be created using the same token. In other words, every time an account should be created, the signup form should be viewed first.