The function ref can allow you to make many useful decision with respect to the type of dereferencing task appropriate for a given segment of the data structure, for example, if 'ref' returned 'ARRAY' when you are looping through a hash you could probably access that particular array by dereferencing it as

foreach my $element (@{$hash{$key}}{
          #work on $element; 
        }
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use strict;
use warnings;
use Data::Dump qw(pp);


my %hash;
push @{$hash{'article'}},{};
$hash{'article'}[0]= {'SKU'=> ['CDS0013'], 'InternalSKU'=>'179', 'Avai
+lableItems'=>['100']};
$hash{'article'}[1]= {'SKU'=> ['CDS0014'], 'InternalSKU'=>'180', 'Avai
+lableItems'=>['102']};
foreach my $key (keys %hash){
        #print ref $hash{$key},"\n";
        foreach my $element (@{$hash{$key}}){
              #  print ref $element,"\n";
                $articleCount = scalar @{$hash{$key}};   #get the coun
+t ...
                foreach my $innerKey(keys %{$element}){
                        print "$element->{$innerKey}","\n";  #some mor
+e referencing yet
                        }
                }
        }
print "there are $articleCount articles\n";
print pp \%hash;
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print $data->{article}[0]{SKU}[0];
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I can reach them like that without problems. I may have described my purpose in a bad way:-)
I can put it like this, I want to find out how many articles there are, so that I loop through them. I.e, I want to be able to do this:

loop over each article, how??
{
    print $data->{article}[i]{SKU}[0];
}
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for my $article (@{$data->{article}}) {
   print $article->{SKU}[0];
}
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I recommend perlreftut, it's easier to read and understand for the not-so-experienced.

Perl 6 - links to (nearly) everything that is Perl 6.

#!/usr/bin/perl

use strict;
use warnings;
use Data::TreeDraw;

my $data = ['article' =>
        {
            'SKU'            => [ 'CDS00013' ],
            'InternalSKU'    => '179',
            'AvailableItems' => [ '100' ]
        },
        {
            'SKU'            => [ 'CDS00014' ],
            'InternalSKU'    => '180',
            'AvailableItems' => [ '102' ]
        }
];
print draw($data), "\n";
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my $AoH = 
          [
              {      
                  'type' => 'article',
                  'SKU' => [ 'CDS00013', ],
                  'InternalSKU' => '179',
                  'AvailableItems' => ['100',],   
              },
                 
              { 
                  'type' => 'article',
                  'SKU' => [ 'CDS00014', ],
                  'InternalSKU' => '180',
                  'AvailableItems' => ['102',],
              },
 
              { 
                 'type' = 'book',
                 'SKU' => [ 'CDS00015', ],
                 'InternalSKU' => '220',
                 'AvailableItems' => ['103',], 
              },
               
           ];
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One fishy thing about the example structure of the OP are sub-elements like
     'SKU' => [ 'CDS00013' ],
and
     'AvailableItems' => [ '100' ]

These imply there may be more than one value associated with each key, but I wonder if it is likely there will be more than one SKU number for a given item. If there will not be, don't put these elements in anonymous arrays.

Of course, the OP example may just be an extreme simplification of a much more complicated structure. If so, it may be worthwhile considering a re-organization of the structure. For instance, if the 'InternalSKU' represents one or more actual, 'external' SKUs (say, from different suppliers, each with its own inventory count), might something like the following be more appropriate for maintainability:

Perhaps How can I visualize my complex data structure? would be helpful to you.

Dear friend,

you can use this below code for accessing actual data..

   #!/usr/bin/perl                                                    
+                                            

use strict;
use warnings;
use Data::Dumper;


my ($hash);

$hash = {
          'article' => [
                       {
                         'SKU' => [
                                        'CDS00013'
                                      ],
                         'InternalSKU' => '179',
                         'AvailableItems' => [
                                        '100',
                                        '200'
                                      ]
                       },
                       {
                         'SKU' => [
                                        'CDS00014'
                                      ],
                         'InternalSKU' => '180',
                         'AvailableItems' => [
                                        '102'
                                      ]
                       }
                     ]
        };
my($key_1,$value,$data);
foreach my $key (keys %$hash){
        foreach my $element (@{$hash->{$key}}){
            
            while (($key_1, $value) = each %$element){
                #print $key_1,"\n";
                if(ref($value) eq "ARRAY") {
                    foreach $data (@{$value}) {
                        print "Actual hash of array data:$data\n"   
                    }   
                }else {
                    print "hash Value:$value\n";
                }   

                
             }

        }
    }
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