extract_extension

# File actionpack/lib/action_controller/caching/actions.rb, line 162
          def extract_extension(request)
            # Don't want just what comes after the last '.' to accommodate multi part extensions
            # such as tar.gz.
            extension = request.path[/^[^.]+\.(.+)$/, 1]

            # If there's no extension in the path, check request.format
            if extension.nil?
              extension = request.cache_format
            end
            extension
          end