Mastering Modern Perl: Writing Efficient and Maintainable Code/

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References and Nested Data Structures

References and Nested Data Structures

Learn more about nested data structures and references.

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Debugging nested data structures

The complexity of Perl’s dereferencing syntax combined with the potential for confusion with multiple levels of references can make debugging nested data structures difficult. The core module Data::Dumper converts values of arbitrary complexity into strings of Perl code, which helps us visualize what we have:

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use Data::Dumper;
my $complex_structure = {
   numbers => [ 1 .. 3 ],
   letters => [ 'a' .. 'c' ],
   objects => {
       breakfast => $continental,
       lunch => $late_tea,
       dinner => $banquet,
   },
};
 
print Dumper( $complex_structure );

This might produce something like the following:

$VAR1 = {
        'letters' => [
                        'a',
                        'b',
                        'c'
                      ],
        'numbers' => [
                        1,
                        2,
                        3
                      ],
        'objects' => {
                'dinner' => bless({...}, 'Dinner'),
                'lunch' => bless({...}, 'Lunch'),
                'breakfast' => bless({...}, 'Breakfast'),
        },
};
Output of the Dumper function

We can use this when we need to figure out what a data structure contains, what we should access, and what we accessed instead. As the elided example alludes to, Data::Dumper can dump objects as well as function ...