But since this is the Stupidest Timeline, the received wisdom for how you spin up a WebSocket server involves installing libraries that will pull in 100k lines of code from whatever the singing-est dancing-est toolkit du jour is, and do you have time to audit that crap? I don't. All this just to let you burp out literally 20 lines of on-the-wire protocol.
Enter Net::WebSocket::Server, which gets my vote. It's tiny and very low level. The documentation was confusing and functional examples nonexistent. However, I eventually figured out how to make it go, and so now you can too:
dna-websock.pl-- It runs separate rooms for each "path" part of the wss: URL. You have access to cookies, so you can plug in your authentication mechanism that way.
websock-post.pl-- It lets you connect, post a notification, disconnect; or sit there and wait for a response for a little while.