perl 排序，字符串排序和数值排序

foreach my $key (sort{$a cmp $b} keys %hash)                                                     
 93 {  
 94     print FOUT "$key:\n";                                                                        
 95     my $rank=1;
 96     foreach my $subkey(reverse sort{$hash{$key}{$a}<=>$hash{$key}{$b}}keys %{$hash{$key}})       
 97     {  
 98         print FOUT "\t$subkey\t$rank\n";                                                         
 99         $rank++;                                                                                 
100     }
101     print FOUT "\n";                                                                             
102 }