my %foo =(
'11' =>{
       '4'=>'Four',
       },
'33' =>{
       '1'=>'One',
       },
'2' =>{
      '2' => 'Two',
      }, 
);
my $ref_HoH = \%foo;
my @sorted = sort {
  my $c = %{ $ref_HoH->{$a} };
  my $d = %{ $ref_HoH->{$b} };
  print "comparing $c to $d...\n";
  $c <=> $d;
} keys %$ref_HoH;
__END__
comparing 1/8 to 1/8...
comparing 1/8 to 1/8...
comparing 1/8 to 1/8...