use warnings;
use strict;
use Test::More tests => 2;

my ($cols,$rows) = (4,3);
my @list = (1..12);

my @AoA = map { [ @list[ $_*$cols .. ($_+1)*$cols-1 ] ] } 0..$rows-1;

is_deeply \@AoA, [[1 .. 4], [5 .. 8], [9 .. 12]]
    or diag explain \@AoA;
is_deeply \@list, [1..12];
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TIMTOWTDI, plenty of other solutions are of course possible. Update: This one assumes that your list fits exactly into the rows and cols that you appear to know beforehand, at least based on your example code.