- handle-not-found #!optional procparameter
The handler for nonexistent files. If the requested URL does not point to an existing file or directory, this procedure is called. It is a procedure of one argument, the path (a string) to the first missing file in the request path. Defaults to a procedure which returns a "404 Not found".
The path path which is passed to the handler is handled in a particular way: It contains all the components that exist, and the final component is the file or directory which does not exist. That means this path may differ from the concatenated URI path; this can be seen as "pathinfo" for the would-be file, if it had existed.
The path should be interpreted as relative to root-path.