I'm not sure if I'm understanding your question, maybe try this:
match '/pr' => 'controller#action' # responds to no additional params
match '/pr/:campaign' => 'another_controller#action' # responds to another param.
So, /pr
will be received by controller#action
, but /pr/test
will be received by another_controller#action
and receive test as params[:campaign]
Edit (actual solution to this problem):
match '/pr' => redirect('/')