The question is if you mutate the variable, create a closure, mutate the variable, create a closure, and so on -- do those closures -- when executed -- each use

The question is if you mutate the variable, create a closure, mutate the variable, create a closure, and so on -- do those closures -- when executed -- each use the value that the variable had at the time the individual closure was created, or do they all use the latest value that the variable had? Scheme (and other academic languages) do the first, Python (and other scripting languages) do the second. But the problem with program comprehensibility comes from doing these gymnastics with block scope and anonymous functions in the first place. The right thing to do is to give things proper names and interfaces. In other words, both what Scheme does and what Python does are bad for reasoning about programs, precisely because the semantics of what should be done in this scenario are implicit and unable to be discerned solely by reading the code. Since either behavior is non-obvious, and understanding the program relies on this implicit behavior, the practice of mutating a variable while repeatedly creating closures over it should be avoided.