(set! resume k2) ; now calling resume with val will ignore val
; and continue with the final line of (begin ... (walk (cdr l)))
; when the next line is executed, yield will be bound to k1 or k3
(set! resume k2) ; now calling resume with val will ignore val
; and continue with the final line of (begin ... (walk (cdr l)))
; when the next line is executed, yield will be bound to k1 or k3