match_extraction

# File actionpack/lib/action_controller/routing/segments.rb, line 218
      def match_extraction(next_capture)
        # All non code-related keys (such as :id, :slug) are URI-unescaped as
        # path parameters.
        default_value = default ? default.inspect : nil
        %[
          value = if (m = match[#{next_capture}])
            URI.unescape(m)
          else
            #{default_value}
          end
          params[:#{key}] = value if value
        ]
      end