No idea about CGI hosting, but I do allow perl 4 (and 3 and 2 and 1) scripts to run on my pastebin, https://perl.bot/ . In this case it's not incompetence but insanity.
Manually patching the source in a few places, most of the time it's just adding a header file or two since some of them predate ANSI C and the standardized header files. The other things have to do with adding -DHAS_... to force them to know that opendir and friends are actually present, so that make install will actually work.
That's also why I added COBOL, that and to test some ideas on how to handle compiled languages on it. The backend service supports multiple files but I haven't finished the web side of things to handle that (I have a strange requirement to make it work without javascript).
If you're after stupid suggestions, would it be "breaking your personal rules" to use only enough Javascript to allow just enough of a transpiled version of the in-browser Java runtime to let '90s vintage Java Applets run? Or maybe Flash?
(And no, I'm 100% not offering to do any of the work required to make that come true... ;-) )
I'd be willing to try something like that, but both flash and java applets are horrendously complex. The javascript restriction is because it's mostly used by us perl developers on irc and there's a few disgruntled greybeards that will actually use it via lynx or links. Closest thing for flash is shumway, https://mozilla.github.io/shumway/ which might be possible to make work but it's still got a lot of compatibility issues from what i hear.
