Tangential curiosity: S-expression languages with lexical binding seem like they still require context-sensitive codewalkers in order to reliably search for patterns that involve any literal symbol that isn't constrained out of that mechanism¹, don't they? What's your strategy for this, just ignore it and hope for the best, or punt to interactive handling for any cases that look slightly tricky? (Or is that still small enough to count as "few lines"?)

¹ For instance, I believe CL forbids lexically binding symbols from the CL package in ways that might conflict with the original definitions. But if you want to find uses of a particular library call from some other non-special package in a sound way, then you have to assume someone might flet that name, due to the way locals work. The underlying codewalker issue is roughly dual to the functioning of non-hygienic macros.