Say, I have a list: 

```
@abc = (5,7,6,2,7,1);

```

I have to obtain a sorted list as well as a sorted list index. So the output will be:

```
@sorted_list = (7,7,6,5,2,1);
@sorted_list_index = (1,4,2,0,3,5);

```

I am also looking a very efficient approach for this problem, since I am actually dealing with a long list with 2^16 entries.