$_ = join "", map { $_ . " " x (8 - length() % 8) } split /\t/, $_, -1;

##</code><code>##

$_ = join "", do {
    my @bits = split /\t/, $_, -1;
    (map { $_ . " " x (8 - length() % 8) } @bits[0..$#bits-1]), $bits[-1]
};