sub print_in_n_cols {
	my ($count, @items) = @_;
	while (@items){
		for (1 .. $count){
			print "\t", shift @items;
			last unless @items;
		}
		print "\n";
	}
}

##</code><code>##

if (@dupes <= 10){
    print_in_n_cols(1, @dupes);
} elsif (@dupes <= 20){
    print_in_n_cols(2, @dupes);
} ...