sub clean_list {

	my $type_of_arg=ref(\@_);

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

	if($type_of_arg eq 'ARRAY')		#if the list is passed as an array
	{
		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;
   			}
		}
	}

	elsif($type_of_arg eq 'REF')	#if the list is passed as a reference to an array
	{
		my %hash;
  		@hash{@{$_[0]}}=();
  		#@{$_[0]}=keys %hash;
  		@array_no_duplicates=keys %hash;
	}

	return (@array_no_duplicates);
}

open(IN, '<', 'ex5.acc') or die "Could not read file\n";
my @initial_array = <IN>;
close IN;
@initial_array = sort @initial_array;

my @final_array = clean_list(@initial_array);  #this works
# @final_array = clean_list(\@initial_array);  #this does not work
# Save the clean table
open(OUT, ">", "ex5.acc.CLEAN") or die "Could not create file\n";
print OUT @final_array;
close OUT;