Understanding Dumper out put

Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

Dear monks,
Please help me understand the Dumper output. This Dumper output is of a scalar that I get from set_sql method of DBI::Class.
I want to know
1) the meaning of each BRACKET ie which means what in this context qw _ ( { [ {},{},{} ] } )
2) Which hash of hash/hash of arrays ?? How to call these (qustion 1,2 are pointing to same thing)
3 How can I push values of each row eg ( 101,John,Scoial_science ) in an array one by one. Following is the Dumper output of scalar from search_set_sql .

$VAR1 = bless( {
                 '_data' => [
                              {
                                'student_id' => '101',
                                'student_name' => 'John',
                                'stream' => 'Social_science',
                              },
                              {
                                'student_id' => '102',
                                'student_name' => 'Smith',
                                'stream' => 'History',
                              }
                            ],
                 '_place' => 0,
                 '_mapper' => [],
                 '_class' => 'School::Block::Student'
               }, 'Class::DBI::Iterator' );
[download]

Please help me to come out of this confusion.

Edit: g0n - code tags in 1)

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Re: Understanding Dumper out put by Joost (Canon) on Dec 15, 2007 at 15:52 UTC
The most important thing to note is that you're dealing with not a plain nested data structure, but an object. You can see that from the `bless( ...., "'Class::DBI::Iterator');` statement surrounding the data structure. The last item in the bless call is the class of the object, in this case Class::DBI::Iterator. If you weren't aware of that, see the docs for that class first. As for the strucure: `{ 'x' => y }` creates a hash reference with 'x' as a key an d y as the value `[ ... ]` creates an array reference `0` is a number `[]` is an reference to an empty array See also perlreftut "What should it profit a man, if he should win a flame war, yet lose his cool?"	[reply] [d/l] [select]

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Re: Understanding Dumper out put
by Joost (Canon) on Dec 15, 2007 at 15:52 UTC

bless( ...., "'Class::DBI::Iterator');

The last item in the bless call is the class of the object, in this case Class::DBI::Iterator. If you weren't aware of that, see the docs for that class first.

As for the strucure:

{ 'x' => y } creates a hash reference with 'x' as a key an d y as the value
[ ... ] creates an array reference
0 is a number
[] is an reference to an empty array