Blacklist certain subdomains from matching URL classes that otherwise allow subdomains to match

[roachcord3]

Fanbox is a good example of this. They allow you to go to https://username.fanbox.cc or https://www.fanbox.cc/@username to get to the same page. Their API is hosted at https://api.fanbox.cc. This means that a URL class for fanbox.cc that matches subdomains will match api.fanbox.cc, which is not desirable, since that's not the gallery URL for an artist. This can lead to situations where it's hard to define a URL class that contains a redirect to a different subdomain of the same domain, since the class will match its own redirect URL.

So, what I'm requesting is either a subdomain blacklist, or, alternatively, allowing users to use regex in the domain part of the URL class (so that they can define something like (?!api\.)([a-z0-9][a-z0-9\-]*\.)?fanbox.cc.