I never realized that a simple loop like this ... actually allocated and destroyed a new array every time through the loop. Since you go around the loop twice, it seems like you don't "leave" the scope in which @a was delcared, so @a should still "be there" during the second iteration. I still don't get that.

In for(...) { ... } the curly braces define a block. Each time the loop iterates you re-enter that block. And every time you enter a block, you enter a new scope.

That is just the way it is, and the way it is meant to be.