sub increment_tuple {
    my ($arg) = @_;

    my $new = [];
    $new->[0] = $arg->[0] + 1;
    $new->[1] = $arg->[1] + 1;
    return $new;
}

my $tuple = [3, 4];
$tuple = increment_tuple($tuple);
print "$tuple->[0] $tuple->[1]\n";