How to keep track of the http referer across requests

application_controller.rb

ApplicationController < ActionController::Base
  before_filter :track_referer


protected
  def track_referer
    @referer = session[:referer] ||= parse_referer(request.headers['HTTP-REFERER'])
  end

  def parse_referer(url)
    ...
  end
end

index.html.erb

<%= main_copy(@referer) %>

info_helper.rb

def main_copy(referer)
  case referer
  when :facebook
    'Some Facebook specific text'
  when :twitter
    'bla'
  end
end