“Staleness” of references, as with “references that will be misinterpreted by the person who tries to follow them,” are simply issues with the Internet at large. Nothing specific to Perl here. We have all read “terse” postings which refer to an Internet article that no longer exists.
Therefore, I’d just suggest ... “don’t particularly [try to] use shortcuts.” Include, for example, the title and author of the web-page that you wish to reference, as well as a brief synopsis of what it says. If you cite a man page, then also <blockquote> the most relevant piece of text that you are intending to cite. In other words, write the comment or post for posterity. Summarize your conclusions. Give your contribution what it will need in order to still be relevant years from now, even if it is “the last man standing.”