swl2 => sub {
        my @list = @input;
        use List::MoreUtils 0.428;
        @list = sort {$a<=>$b} @list;
        my $i = List::MoreUtils::bsearchidx {$_ <=> 0} @list;
        if ($i < 0) {  #  no zero
            $i = List::MoreUtils::firstidx {$_ >= 0} @list;
        }
        else {
            $i-- while !$list[$i];
            $i++;
        }
        push @list, splice @list, 0, $i;
        Compare(\@list,\@output) or die "@list" if DO_CHECK;
    },