title: Codeigniter route "mysite.com/$username" to "users/profile/username"
body: <p>I want to load a profile of user from "users/profile/username" where username is same as $username (without $ sign), How can I define rule for this routing?</p>
  
  <p>I do want to keep "$" in my url for some reason.</p>
  
  <p>it means when mysite.com/$username is typed, CI will route this request to mysite.com/users/profile/username (no $ sign now, as it is just to identify that the request is for 'username' and its not a controller)</p>