B.2 Nested Data Structures

Each array or hash is a collection of scalars, some or all of which can be references to other structures.

7. Lists do not nest like this:

   @foo = (1, 3, ("hello", 5), 5.66);

   For nesting, make the third element a reference to an anonymous array:

   @foo = (1, 3, ["hello", 5], 5.66);
         

8. An example of a nested data structure (a hash of array of hashes):

   $person = {   # Anon. hash
      "name" => "John",  # '=>' is an alias for a comma
      "age"  => 23,
      "children" => [  # Anonymous array of children
                        {
                           "name" => "Mike",  "age"  => 3,
                        },
                        {
                           "name"  => "Patty","age"   => 4
                        }
                    ]
      };
   print $person->{age}                 ; # Print John's age
   print $person->{children}->[0]->{age}; # Print Mike's age
   print $person->{children}[0]{age}    ; # Print Mike's age, omitting
                                          # arrows between subscripts

9. To pretty-print $person above:

    use Data::Dumper;
    Data::Dumper->Dumper($person);
    # Or,
    require dumpVar.pl;
    main::dumpValue($person);