Just for fun...

#!/usr/bin/perl

use strict; # https://perlmonks.org/?node_id=11125178
use warnings;

my @list = 1 .. 12;
my @AoA = [];
my $C = 4;

push @{ @{ $AoA[-1] } < $C ? $AoA[-1] : \@AoA },
  @{ $AoA[-1] } < $C ? $_ : [ $_ ] for @list;

use Data::Dump 'dd'; dd \@list; dd \@AoA;
[download]

Outputs:

[1 .. 12]
[[1 .. 4], [5 .. 8], [9 .. 12]]
[download]