the #hash part for deep-linking to anchors
Oh... So you're not talking about path parts. You're talking about fragment parts —
So in some sense this is a form of link rot. I think there will always be some risk of this, since we don't have any control over how any external web site manages their anchors
— nor indeed their paths — nor indeed even the domain names.
It's the nature of the beast. People put external links in their posts; ten years later those links don't work. We just have to live with the risk.
In general, I'd prefer to stay with perldoc.perl.org, since it is "official". I think we'd need a really compelling reason to switch to something else. Like we did with MetaCPAN.
I reckon we are the only monastery ever to have a dungeon stuffed with 16,