#!/usr/bin/env perl
use strict;
use warnings;
use 5.016;
use Data::Dumper;

my $data = "1ABCD2EFGH3IJKL4MNOP5QRST6UVWX";
my $entry_size = 5;
my @items = unpack "(a$entry_size)*", $data;
my @out = map { [unpack "CA*"] } @items;

print Dumper \@out;