The invariable rules are a rulebook.
The invariable rulebook has a room called the foo-place.
The bar is a room.
but rejects
The invariable rules are a rulebook.
The invariable rulebook has a room called the foo-place (matched as "foo").
The bar is a room.
with the error
Unless such variable tokens are now restricted to actions such as in The going action has a room called the room gone from (matched as “from”), I suspect a bug.
Similar code was used with 6G60 in Version 2 of Restrictions by Jon Ingold.