#!/usr/local/bin/perl -w

use strict;
my  ( @temp, %authors );
@temp = sort map { my @b=split; $b[2]; } `ls -l /directory/pth/here`;
foreach ( @temp )
{
   $authors{$_}=1 if not $authors{$_} and length $_; 
#I had to add $_ because the other way "$authors{$}=1" gave me an error
}
print "$_\n" for keys %authors;