use warnings;
use strict;

use Data::Dumper;

my $mref = [ [ '5', '4', '4', '2', '4' ],];

my @data;

  for (@$mref){
    push @data, map {[$_]} @{$_}
  }

print Dumper \@data;

##</code><code>##

$VAR1 = [
          [
            '5'
          ],
          [
            '4'
          ],
          [
            '4'
          ],
          [
            '2'
          ],
          [
            '4'
          ]
        ];