my @AoA = ([1, 2, 3], [4, 5, 6], [7, 8, 9]);
for my $row (@AoA) {
    my ($sum, $count) = (0, 0);
    for my $col (@$row) {
        $sum +=  "$col ";
        $count ++;
    }
    print "Average: ", $sum / $count, "\n" if $count;
}