You have an off-by-one error here.

$ perl -MData::Dumper -e '
> my @array = (1, 2, 3, 4, 5, 6, 7, 8);
> my @new_array = map{ [$array[2 * $_ - 1], $array[2 * $_]] } 1 .. @ar
+ray/2;
-> print Dumper(\@new_array);'
$VAR1 = [
          [
            2,
            3
          ],
          [
            4,
            5
          ],
          [
            6,
            7
          ],
          [
            8,
            undef
          ]
        ];
$
[download]

This works.

$ perl -MData::Dumper -e '
> my @array = (1, 2, 3, 4, 5, 6, 7, 8);
> my @new_array = map{ [$array[2 * $_], $array[2 * $_ + 1]] } 0 .. $#a
+rray/2;
-> print Dumper(\@new_array);'
$VAR1 = [
          [
            1,
            2
          ],
          [
            3,
            4
          ],
          [
            5,
            6
          ],
          [
            7,
            8
          ]
        ];
$
[download]

Cheers,

JohnGG