In Perl, there are 3 different kinds of hashes.

• A regular hash, which is defined by the % and ( ) characters - %hash = ( );
• A reference hash, which is defined with the $ and { } characters = $hash = { };
• A hash array, which is defined with the % and [ ] characters - %hash = [ ];

Let's say you want to create a hash that has two (or more) keys, like this. In this example, the bar key is a child of the foo key.

'foo' {
        'bar' => 'Hello World'
      }

Here is how you can create the multidimensional keys and value.

my %hash = ( 'foo' => { 'bar' => 'Hello World' } );

Or like this.

my $hash{foo}->{bar} = "Hello World";

Dumper can be used to print the hash.

print Dumper \%hash;

Which will produce the following.

$VAR1 = {
          'foo' => {
                     'bar' => 'Hello World'
                   }
        };

Or to print the value of the bar key.

print $hash{foo}->{bar};

Which will produce the following.

Hello World