[kazinator]

But stuff like

   (let (var1 (var2 0))
     (when condition
       (setq var1 (var1-initializer-form))
        ...)))

is just silly. Only the inner scope of the when uses var1, or any of the vars; it could just be:

   (when condition
     (let ((var1 (var1-initializer-form))
           (var2 0))
        ...))

Never do two-step initialization of a variable without an excellent reason; it's just sloppy otherwise.