I don't know about the borrowing system, but I believe there are several Lisps that avoid mark-sweep garbage collection. NewLisp is one such example, though I t

I don't know about the borrowing system, but I believe there are several Lisps that avoid mark-sweep garbage collection. NewLisp is one such example, though I think they sidestep the issue by copying everything by default and using efficient allocation/deallocation.