It really seems like there ought to be a quicker explanation for this, but to explain the fundamental goals, the pitfalls, and the usage constraints of this data type… well, data types are hard to explain if they’re off the beaten path. This one is really useful, but also pretty strange.
edit: Aaaand Badger figured out the bug, which was not in this code, while I was making the video. Hopefully someone else finds this useful or interesting. ;)