-- httpd first searches for a resource in the tree, and then calls
-- fallback handlers to ask them for a resource. If all of the
-- handlers returned 'Nothing', the httpd responds with 404 Not Found.
-- httpd first searches for a resource in the tree, and then calls
-- fallback handlers to ask them for a resource. If all of the
-- handlers returned 'Nothing', the httpd responds with 404 Not Found.