my @keys = reverse sort {$hash{$a} <=> $hash{$b} || $a cmp $b} (keys %hash);
foreach my $i ( 0 .. int($#keys/2) ){
  # printf "%s %s\n", @keys[$i, $i+int($#keys/2)+1];

  # UPDATE: expanded to avoid 'uninitialized value' warning
  print $keys[$i];
  my $j = $i+int($#keys/2)+1;
  print "\t" . $keys[$j] if $j <= $#keys;
  print "\n";
}