You should imagine variables as tentacles, rather than boxes. They do not contain values; they grasp them – two variables can refer to the same value. Only the values that the program still has a hold on can be accessed by it. When you need to remember something, you grow a tentacle to hold on to it, or you reattach one of your existing tentacles to a new value.
From the publisher, No Starch Press: It’s available in a couple of forms…
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