my $buf;
my @out = ();
while ( length( $bigstring )) {
    $buf = '';
    $buf = $buf . chop $bigstring for (0..2);
    for (0..3) { 
        push @out, ($buf & 64); # update: Perl didn't accept this bit op
        $buf >>= 6; # but is happy with this one
    }
}