A few things spring to mind:

1. please use < code > < / code > tags
2. if you want the count of items in the array, use scalar(@array)
3. you appear to be counting from 1, but Perl arrays start at 0 (zero)
4. generally, the easy way to avoid duplicates is to store the data in a hash eg
$my_hash{$my_6digits} = 1;

Cheers
Chris