#!/usr/bin/perl

use strict;
use warnings;

# store 'A' and 'B' as a bitstream
# (bit groups are stored big endian!)
my @bits = (
  1, 0, 0, 0, 0, 0, 1, 0,   # A / 0x41 / 0b01000001
  0, 1, 0, 0, 0, 0, 1, 0,   # B / 0x42 / 0b01000010
  1, 1, 0, 0, 1, 0, 1       # incomplete byte
);

my $data;
while (@bits >= 8) {
  # fetch bit group
  my @eightbits_be = splice @bits, 0, 8;
  # convert to little endian
  my @eightbits_le = reverse @eightbits_be;
  # generate binary representation 
  my $binary       = '0b' . join q{}, @eightbits_le;
  # convert binary representation into actual value
  my $value = chr oct $binary;

  $data .= $value;
}

printf "data: %s\n", $data;                # AB
printf "bits: %s\n", join ', ', @bits;     # 1, 1, 0, 0, 1, 0, 1