sub mark_attacks {
   my ($r,$c,$array) = @_;

   $array->[$r]->[$c] = 'Q';

   # mark everything

   my $none;

   for my $i (1 .. $SIZE) {
      $none = 1;
      $none = $array->[$r]->[$c + $i] = 0 if ($c + $i < $SIZE);
      $none = $array->[$r]->[$c - $i] = 0 if ($c - $i >= 0);
      $none = $array->[$r + $i]->[$c] = 0 if ($r + $i < $SIZE);
      $none = $array->[$r - $i]->[$c] = 0 if ($r - $i >= 0);
      $none = $array->[$r - $i]->[$c - $i] = 0 if ($r - $i >= 0 and $c - $i >= 0);
      $none = $array->[$r + $i]->[$c + $i] = 0 if ($r + $i < $SIZE and $c + $i < $SIZE);
      $none = $array->[$r - $i]->[$c + $i] = 0 if ($r - $i >= 0 and $c + $i < $SIZE);
      $none = $array->[$r + $i]->[$c - $i] = 0 if ($r + $i < $SIZE and $c - $i >= 0);
      last  if $none;
   }
}