Sometimes in #Lisp #Programming, particularly #MetaProgramming, though admittedly rarely, there arises a need to have an expression considered to be in a higher lexical environment (i..e. excluding one or more immediately enclosing environments). A special case of that is to consider the expression to be in the top-level environment).
I've come up with a nice formalism that is easy to retrofit with a low amount of work: the in-env-above operator.
(in-env-above x e1 e2 e3 ...)
searches the environment for variable x, and removes every environment frame it traverses. Then expressions e1 e2 ... are expanded and evaluated in the remaining environment chain. if x is not found, they are in the top-level environment. We allow x to be nil to express that intent.
By identifying the target env using a variable binding expected to be in it, we eliminate the need to implement an extra identifying mechanism, or using relative addressing like "3 levels up".
Macros often introduce gensyms; one of those can be used.