use MIME::Base64 qw( decode_base64 );

  my $scrambled = decode_base64($_);
  my @scrambled = unpack('C*', $scrambled) ;
  my @orig      = map { $scrambled[$_-1] ^ $scrambled[$_] } 1..$#scrambled;
  my $orig      = pack('C*', @orig) ;

##</code><code>##

  my $b = "123\xC4" ;
  my $u = "a\xC4\x{107}\x{1C4}" ;

  show(unpack('C*',   $b)) ;  # 0x31, 0x32, 0x33, 0xC4
  show(unpack('C*',   $u)) ;  # 0x61, 0xC4, 0x107, 0x1C4

  { use bytes ;
    show(unpack('C*', $b)) ;  # 0x31, 0x32, 0x33, 0xC4
    show(unpack('C*', $u)) ;  # 0x61, 0xC3, 0x84, 0xC4, 0x87, 0xC7, 0x84
  } ;

  sub show {
    print join(", ", map(sprintf("0x%02X", $_), @_)), "\n" ;
  } ;

##</code><code>##

  my $u = "a\xC4\x{107}\x{1C4}" ;

  my @u = unpack('C*', $u) ;
  show(@u) ;                  # 0x61, 0xC4, 0x107, 0x1C4
  bytes(pack('C*',@u)) ;      # Character in 'C' format wrapped in pack ...
                              # Character in 'C' format wrapped in pack ...
                              # 61:C4:07:C4 -- byte

  sub show {
    print join(", ", map(sprintf("0x%02X", $_), @_)), "\n" ;
  } ;

  sub bytes {
    my ($s) = @_ ;
    my $w = utf8::is_utf8($s) ? "utf8" : "byte" ;
    use bytes ;
    print join(":", map(sprintf("%02X", $_), unpack('C*', $s))), " -- $w\n" ;
  } ;