my @keys = sort { $hash{$b} <=> $hash{$a} || $b cmp $a } keys %hash;

my $half = int($#keys / 2);

printf "%s\t%s\n", @keys[$_, $_+$half]
   for 0 .. $half-1;

printf "%s\n", $keys[$#keys]
   unless $#keys % 2;