How does World (DX11.Layer) work?

I have discovered this fancy node. Why does it work on some layers / effects and not on others? What does a shader need to implement in order to work with that node?

There‘s a couple of custom semantics …
The transform you’ll want to use needs to make use of these:
WORLDLAYER
WORLDLAYERVIEW
WORLDLAYERVIEWPROJECTION
and so on.