package Foo;

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) = @_;
    printf "  Before %s [%s]\n", $d, join(",", @$d);
    $Foo::d = [];
    printf "  After %s [%s]\n", $d, join(",", @$d);
});

--(0)> perl test.pl
Top before ARRAY(0x8144234) [a,b]
  Before ARRAY(0x8144234) [a,b]
  After ARRAY(0x8144234) [a,b]
Top After ARRAY(0x81442dc) []