if ( $dr4 < 0 ) {
           #pre-populate deletion array;
           my @delarray = ( 0 .. $chntot );
           @dlarray = shuffle @delarray;

           my $cndiea = 0;
           foreach my $del ( 0 .. $chntot ) {
               if ( $aod[$del][$yb] eq 'd' ) {
                   $cndiea++;
               }
           }
           my $cnr = $cndiea;
           for my $xd ( 0 .. $chntot ) {
               my $xda = $dlarray[$xd];
               if ( $aod[$xda][$yb] eq 'a' && $cnr < $incrsdel ) {
                   $aod[$xda][$yb] = 'd';
                   $cnr++;
               }
           }
       }