#!/usr/bin/perl
use v5.14;
use warnings;

my $packed_bytes = "ABCD";
my @bytes = unpack 'C*', $packed_bytes;

my $bin = '';
for my $byte ( @bytes ) {
   printf "Decimal = [%1\$d]  Hex = [%1\$02X]  Binary = [%1\$08b]\n",
      $byte;

   $bin .= sprintf( "%08b", $byte );
}

say "";
say $bin;