# initialisation as before

$cur = $best = $array[$cur_start] if @array;

for (1..$#array) {
  $cur += $array[$_];
  if ($best < $cur) {
    $best = $cur;
    $best_start = $cur < 0 ? $_ : $cur_start;
    $best_end = $_;
  }
  elsif ($cur < 0) {
    $cur = 0;
    $cur_start = $_ + 1;
  }
}