In the revsort example, the input file format is https://www.iana.org/assignments/media-types/text/plain, but that page does not exist. I'm not even sure this is a problem: is that supposed to lead to an actual web page? Or is there a reference doc stating that's the correct URI? Would https://www.rfc-editor.org/rfc/rfc2046.html#section-4.1.3 be a viable URL alternative?