rand(0 .. $total)

##</code><code>##

rand($total+1)

##</code><code>##

rand(0+@aob)

##</code><code>##

while (1) {
    my $xda = int rand( 0+@aob );
    if ( $aob[$xda][ $y - 1 ] ne "") {
        $aob[$x][$y] = $z + $aob[$xda][ $y - 1 ];
        last;
    }
}