Question 2 

my $line = '';
foreach my $i (1..length($bytes)) {
    my $char = ord substr($bytes, $i - 1, 1);
    $line .= encode_bits($char >>  4) . ' ';
    $line .= encode_bits($char &  15) . ' ';
    if(length($line) > 80) {
        print $line, "\n";
        $line = '';
    }
}
print $line, "\n";

sub encode_bits {
    my($bits) = @_;

    my $el = $nyb{$bits};
    return $el->[ rand($#{$el}) ];
}