sub st_sort_substr {
    @{[
        map $_->[0],
        sort {
            $a->[1] <=> $b->[1]
        }
        map [$_, substr $_, 2], @unordered
    ]};
}

sub map_cat_substr_expr {
    @{[
        map "a-$_",
        sort {
            $a <=> $b
        }
        map substr($_, 2), @unordered
    ]};
}