Don't do that. But, like this:

foreach (keys %var) {      ## Here $_ will have a , b
    foreach ( map [scalar each %{$var{$_}}, $_], ($_) x keys %{$var{$_
+}} ) {
        print "inner '\$_': $_->[0]\n";
        print "outer '\$_': $_->[1]\n";
    }
    keys %{$var{$_}}; # iterator reset
}
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