| 
| handwaving here... starting with @ry1 and @ry2 being fully populated.
for($i=0;$i<=($#ry1 < $#ry2? $#ry1 : $#ry2){
    if ($ry1[$i] != 0 ) {
             $ry[$i] = <do something> # edit accordingly
    }
}