#!perl -lw
$x = "\x55\xAA\x55\xAA";;
substr( $x, $_, 1 ) = chr( ord( substr( $x, $_, 1 )) << 1 ) for 0 .. 3;;
my $ox = $x;
print unpack 'b*', $x;;
print unpack 'U0b*', $x;;
print unpack 'C0b*', $x;;
__END__
Character in 'b' format wrapped in unpack at - line 5.
Character in 'b' format wrapped in unpack at - line 5.
01010101001010100101010100101010
0100001101010101101000110010100101000011010101011010001100101001
Character in 'b' format wrapped in unpack at - line 7.
Character in 'b' format wrapped in unpack at - line 7.
01010101001010100101010100101010
##</code><code>##

$ perl
#!perl -lw
$x = "\x55\xAA\x55\xAA";;
substr( $x, $_, 1 ) = chr( ord( substr( $x, $_, 1 )) << 1 ) for 0 .. 3;;
my $ox = $x;
use bytes;
print unpack 'b*', $x;;
print unpack 'U0b*', $x;;
print unpack 'C0b*', $x;;
__END__
0100001101010101101000110010100101000011010101011010001100101001
11000011010000010100001101010101110000111010000101000011001010011100001101000001010000110101010111000011101000010100001100101001
0100001101010101101000110010100101000011010101011010001100101001