In this example, we use the page_matches function to define two custom routes. The first route matches any URL that starts with '/blog/' and is followed by a number, and the second route matches any URL that starts with '/category/' and is followed by any characters. These custom routes are defined as callback functions that will be executed when the URL matches the pattern. The $matches parameter is an array containing any captured groups from the regular expression match. The package library for this function is likely to be a PHP micro-framework or routing library. Examples of such packages include Slim, Lumen, and Flight.