swl3 => sub {
        my @list = @input;
        use List::MoreUtils 0.428;
        @list = sort {$a<=>$b} @list;
        if ($list[0] < 0 && $list[-1] >= 0) {
            my $i = List::MoreUtils::bsearchidx {$_ <=> 0} @list;
            if ($i < 0) {  #  no zero, find first positive
                $i = 0; $i++ while ($list[$i]<0);
            }
            else {  #  find start of zeroes
                $i-- while !$list[$i];
                $i++;
            }
            push @list, splice @list, 0, $i;
        }
        Compare(\@list,\@output) or die "@list" if DO_CHECK;
    },