$ref = [
    map  { $_->[0] }
    sort { $a->[1] cmp $b->[1] }
    map  { my $srn = lc $_->seq_region_name;
          [ $_, pack "sA*", $srn =~ /^[0-9]+$/ ? $srn : 999, $srn ]
          }
    @$ref ];