You mention similarity to PHP already, but you may not know that in 1999 PHP supported <script language="php"></script> too! I’m not sure if PHP still does.
ASP had runat="server".
Thankfully that was removed in the 7-series. Possibly 7.0.0?
I’ve never liked this idea of abusing HTML tags and embedding another language into your page (with the exception of the <script> tag). It feels like a step backwards :D
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Maybe the goal is to have fun :-)
My pet project does it better. Specifically, it allows you to pipe any element identifiable with a CSS selector through any external program, and pass any attributes to that program.
Not arguing that Deno is a great project though, I’m planning to use it myself for some scripts.