>perl -wMstrict -le
"my $data = q{'A','B','C','D','E','F','G','H','I','J','K','L','M'};
 ;;
 my @ra = split m{ (?: , [^,]+){3} \K , }xms, $data;
 ;;
 printf qq{:$_:  } for @ra;
"
:'A','B','C','D':  :'E','F','G','H':  :'I','J','K','L':  :'M':

##</code><code>##

>perl -wMstrict -le
"use List::MoreUtils qw(natatime);
 use Data::Dumper;
 ;;
 my @data = ('A','B','C','D','E','F','G','H','I','J','K','L','M');
 ;;
 my $it = natatime 4, @data;
 my @groups;
 while (my @group = $it->()) {
   push @groups, \@group;
   }
 print Dumper \@groups;
"
$VAR1 = [
          [
            'A',
            'B',
            'C',
            'D'
          ],
          [
            'E',
            'F',
            'G',
            'H'
          ],
          [
            'I',
            'J',
            'K',
            'L'
          ],
          [
            'M'
          ]
        ];