my @list = qw( one two three one );
@list = make_unique( @list );

sub make_unique {

	my @list = @_;
	my %seen;
	my @new_list;

	foreach my $item ( @list ) {
		if ( not defined $seen{$item} ) {
			$seen{$item} = 1;
			push @new_list, $item;
		} else {
			push @new_list, $item . '_' . $seen{$item};
			$seen{$item}++;
		}
	}

	return @new_list;
	
}