my $text2 = "$text$text";
my $bwt4 = join('', 
		map{substr($text, ($_ - 1), 1)} 
		map{ $_->[0] }
		sort{ ${$a->[1]} cmp ${$b->[1]} }
		map{ 
		  [$_,\substr($text2,$_,$ntext)]
		} 0..$ntext-1
);
print "$text: $bwt4\n";