Another way to do it... but it only works if all the numbers have the same number of digits.... :) but anyway...

my $sorted = [ sort {
    $a->{under} . $a->{order} cmp $b->{under} . $b->{order}
} @$aoh ];
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I wonder if there's some way to hack this into something that actually would work, using sprintf %dd or something?... Actually, I don't wonder. Never mind...