# File lib/mini_mime.rb, line 100
      def lookup(val)
        @hit_cache.fetch(val) do
          @miss_cache.fetch(val) do
            data = lookup_uncached(val)
            if data
              @hit_cache[val] = data
            else
              @miss_cache[val] = nil
            end

            data
          end
        end
      end