What I mean, Toby, is just that “within the Perl system, most-specifically versus the PHP system,” there is n-o concept of the language-interpreter being “embedded within” a surrounding file “that is to be served.” Although this concept is a foundation of PHP, I can’t readily recall any other language which does the same thing.
Still, you quite-correctly heap coals upon the same fire: there are, in fact, a great many differences between the two languages which would make a transliteration between them ... let alone an automatic one ... quite difficult to achieve satisfactorily. And this may well be the best answer to the OP’s question: “Even if it could be done, it’s just not worth doing.” We don’t have to do it. There is no advantage to be had in picking that particular fight. We have all of these language systems at our beck-and-call, side by side. We can, when we need to, make them work together.