timethese($ARGV[0]||-1, {
    hash => sub { $foo->set_name("x");return $foo->get_name },
    array => sub { $bar->set_name("x");return $bar->get_name },
    });
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$foo is a blessed hash and $bar a blessed array. both have 15 attributes. the array subroutine takes about 93% of the time.

memory saving depends, of course, on the length of the hash keys. with 15 hash keys of length 5 i save about 15% 35%. (measured with Devel::Size::total_size)

edit: i measured wrong for the memory test. i was just copying references before.