use Data::Dumper;
use Tie::IxHash;
tie my %hash_ref, 'Tie::IxHash' ;

%hash_ref = (
             'MAIN' => {
                        'ZOP' => 
                                {'Dev', undef, 
                                'Con', undef, 
                                'Test', undef, 
                                'Exit', undef, 
                                'New', undef },
                        'AP' => 
                                {'Dev', undef, 
                                'Con', undef, 
                                'Test', undef, 
                                'Exit', undef, 
                                'New', undef }, 
                         'Exit' => undef,                               
          
                         }
             );
print Dumper(\%hash_ref); 

##</code><code>##

use Data::Dumper;
use Tie::IxHash;
tie my %list1, 'Tie::IxHash' ;
tie my %list2, 'Tie::IxHash' ;
tie my %hnr, 'Tie::IxHash' ;

%list1 = ( 'ZOP',undef,'AP',undef, 'Exit', undef );
%list2 = ( 'Dev',undef, 'Con', undef, 'Test', undef, 'Exit', undef, 'New', undef);
$hnr{'MAIN'} = { %list1 };
$hnr{'MAIN'}{'ZOP'} = { %list2 };
$hnr{'MAIN'}{'AP'} = { %list2 };

print Dumper(\%hnr); 

##</code><code>##

tie my %myhash, 'Tie::IxHash';

%myhash = ( 'ne', undef, 
            'na', undef,
            'e', undef, 
            'a', undef, 
            'z', undef, 
            'h', undef,
             2, undef,
             5, undef, 
            12, undef,  
             7, undef);
print Dumper(\%myhash);