Make a subroutine that removes duplicates from a list. If the list is passed as an array, then return a clean list. If the list is passed as a reference to an array then clean the given array in place.

##</code><code>##

sub clean_list {

	my @array_with_duplicates=(@_);
	my @array_no_duplicates;

	my $previous = '';
	while (scalar @array_with_duplicates > 0) 
	{
   		my $next = shift(@array_with_duplicates);
   		if ($previous ne $next) 
   		{
     		push(@array_no_duplicates, $next);
     		$previous = $next;
   		}
	}


##</code><code>##

open(IN, '<', 'myfile') or die "Could not read file\n";
my @array_with_duplicates = <IN>;
close IN;
@array_with_duplicates = sort @array_with_duplicates;

clean_list(@array_with_duplicates);

open(OUT, ">", "myfile.NO_DUPLICATES") or die "Could not create file\n";
print OUT @array_no_duplicates;
close OUT;


##</code><code>##

sub clean_array 
{
  my %hash;
  @hash{@{$_[0]}}=();
  @{$_[0]}=keys %hash;
}


##</code><code>##

open(IN, '<', 'myfile') or die "Could not read file\n";
my @initial_array = <IN>;
close IN;

clean_array(\@initial_array); 

open(OUT, ">", "myfile.NO_DUPLICATES") or die "Could not create file\n";
print OUT @initial_array;
close OUT;