Concerning your first question, the output you get is exactly what I was expecting when reading the code. While I can't really think of any use for such a strange construct, clearly the
local keyword modifies the hash to be "local" to the enclosing
do block. So that the code populates each time a local copy of
%h and retrieves a reference to this local copy of the hash and assigns this reference to
$x and
$y. As soon as the code leaves the
do block, the value of the hash is reset to its original empty value.
I may be wrong, but I can't see why it wouldn't be safe to do that. And I don't even think it is magic.
Or did I perhaps miss something about your concerns?
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