package Foo;
our $d;              #the only line added

sub top {
    my($fn) = @_;
    our($d) = ["a", "b"];
    printf "Top before %s [%s]\n", $d, join(",", @$d);
    $fn->($d);
    printf "Top After %s [%s]\n", $d, join(",", @$d);
}


package Bar;

Foo::top(sub {
    #our($d) = @_;  #removed!
    printf "  Before %s [%s]\n", $d, join(",", @$d);
    $d = [];
    printf "  After %s [%s]\n", $d, join(",", @$d);
});