my ($C,$R)=(4,3); #Columns,Rows

my @list = qw(1 2 3 4 5 6 7 8 9 10 11 12);
my @AoA=();

while (@list) { push(@AoA, [ splice(@list, 0, $C) ]);  }

pp \@AoA;
pp \@list;
[[1 .. 4], [5 .. 8], [9 .. 12]]
[]