Nested Bless within Hash of Arrays

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

BACKGROUND: I'm using XML::Compile::Schema to read multiple xsd files and generate a hash of the contents with the template function.

my $xsd=XML::Compile::Schema->new(\@array);
my $t= $xsd->template('TREE',$xsd->elements());
print LOG Dumper($t);
[download]

The resulting LOG shows:

$VAR1 = {
          'attrs' => [],
          ...
          'elems' => [
                       bless( {
                                'struct' => [...],
                                'elems' => [
                                             {
                                               ...
                                             },
                                             {
                                               'attrs' => [],
                                               'elems' => [
                                                            bless( {
                                                                     '
+struct' => [...],
                                                                     '
+elems' => [
                                                                      
+            {
                                                                      
+              ...
                                                                      
+            },
                                                                      
+            {
                                                                      
+              'attrs' => [],
                                                                      
+              'elems' => [
                                                                      
+                           bless( {
                                                                      
+                                    'struct' => [
                                                                      
+                                                  ...
                                                                      
+                                                ],
                                                                      
+                                    'elems' => [
                                                                      
+                                                 {
                                                                      
+                                                   ...
                                                                      
+                                                 },
                                                                      
+                                                 {
                                                                      
+                                                   'attrs' => [],
                                                                      
+                                                   'elems' => [
                                                                      
+                                                                bless
+( {
                                                                      
+                                                                     
+    'struct' => [
                                                                      
+                                                                     
+                  ...,
                                                                      
+                                                                     
+    'elems' => [
                                                                      
+                                                                     
+                 {
                                                                      
+                                                                     
+                  ...                                                
+                                                                     
+    },
                                                                      
+                                                                     
+                 {
                                                                      
+                                                                     
+                   ...
                                                                      
+                                                                     
+                 },
                                                                      
+                                                                     
+                 {
                                                                      
+                                                                     
+                   ...
                                                                      
+                                                                     
+                 }
                                                                      
+                                                                     
+               ],
                                                                      
+                                                                     
+    'tag' => 'sequence'
                                                                      
+                                                                     
+  }, 'BLOCK' )
                                                                      
+                                                              ],
                                                                      
+                                                   ...
                                                                      
+                                                 },
                                                                      
+                                                 {
                                                                      
+                                                   'attrs' => [],
                                                                      
+                                                   'elems' => [
                                                                      
+                                                                bless
+( {
                                                                      
+                                                                     
+    ...,
                                                                      
+                                                                     
+    'elems' => [
                                                                      
+                                                                     
+                 {
                                                                      
+                                                                     
+                   'attrs' => [],
                                                                      
+                                                                     
+                   'elems' => [
                                                                      
+                                                                     
+                                bless( {
                                                                      
+                                                                     
+                                         'struct' => [...],
                                                                      
+                                                                     
+                                         'elems' => [
                                                                      
+                                                                     
+                                                      {...},
                                                                      
+                                                                     
+                                                      {...}
                                                                      
+                                                                     
+                                                    ],
                                                                      
+                                                                     
+                                         'tag' => 'sequence'
                                                                      
+                                                                     
+                                       }, 'BLOCK' )
                                                                      
+                                                                     
+                              ],
                                                                      
+                                                                     
+                   ...
                                                                      
+                                                                     
+                 },
                                                                      
+                                                                     
+                 {
                                                                      
+                                                                     
+                  ...
                                                                      
+                                                                     
+                 }
                                                                      
+                                                                     
+               ],
                                                                      
+                                                                     
+    'tag' => 'sequence'
                                                                      
+                                                                     
+  }, 'BLOCK' )
                                                                      
+                                                              ],
                                                                      
+                                                   ...
                                                                      
+                                                 },
                                                                      
+                                                 {
                                                                      
+                                                   'attrs' => [],
                                                                      
+                                                   'elems' => [
                                                                      
+                                                                bless
+( {
                                                                      
+                                                                     
+    'struct' => [
                                                                      
+                                                                     
+                 ...
                                                                      
+                                                                     
+                ],
                                                                      
+                                                                     
+    'elems' => [
                                                                      
+                                                                     
+                 {
                                                                      
+                                                                     
+                  ...                                                
+                                                 },
                                                                      
+                                                                     
+                 {
                                                                      
+                                                                     
+                  ...
                                                                      
+                                                                     
+                 },
                                                                      
+                                                                     
+                 {
                                                                      
+                                                                     
+                   ...
                                                                      
+                                                                     
+                 }
                                                                      
+                                                                     
+               ],
                                                                      
+                                                                     
+    'tag' => 'sequence'
                                                                      
+                                                                     
+  }, 'BLOCK' )
                                                                      
+                                                              ],
                                                                      
+                                                   ...
                                                                      
+                                                 },
                                                                      
+                                                 {
                                                                      
+                                                   'attrs' => [],
                                                                      
+                                                   'elems' => [
                                                                      
+                                                                bless
+( {
                                                                      
+                                                                     
+    'struct' => [
                                                                      
+                                                                     
+                  ...
                                                                      
+                                                                     
+                ],
                                                                      
+                                                                     
+    'elems' => [
                                                                      
+                                                                     
+                 {
                                                                      
+                                                                     
+                   ...
                                                                      
+                                                                     
+                 }
                                                                      
+                                                                     
+               ],
                                                                      
+                                                                     
+    'tag' => 'sequence'
                                                                      
+                                                                     
+  }, 'BLOCK' )
                                                                      
+                                                              ],
                                                                      
+                                                   ...
                                                                      
+                                                 },
                                                                      
+                                                 {
                                                                      
+                                                   ...
                                                                      
+                                                 }
                                                                      
+                                               ],
                                                                      
+                                    'tag' => 'sequence'
                                                                      
+                                  }, 'BLOCK' )
                                                                      
+                         ],
                                                                      
+             ...
                                                                      
+            }
                                                                      
+          ],
                                                                     '
+tag' => 'sequence'
                                                                   }, 
+'BLOCK' )
                                                          ],
                                              ...
                                             },
                                             {
                                               'attrs' => [],
                                               'elems' => [
                                                            bless( {
                                                                     '
+struct' => [
                                                                      
+            ...
                                                                      
+           ],
                                                                     '
+elems' => [
                                                                      
+            {
                                                                      
+              'attrs' => [],
                                                                      
+              'elems' => [
                                                                      
+                           bless( {
                                                                      
+                                    'struct' => [
                                                                      
+                                                 ...
                                                                      
+                                                ],
                                                                      
+                                    'elems' => [
                                                                      
+                                                 {
                                                                      
+                                                   ...
                                                                      
+                                                 },
                                                                      
+                                                 {
                                                                      
+                                                   ...
                                                                      
+                                                 },
                                                                      
+                                                 {
                                                                      
+                                                   ...
                                                                      
+                                                 },
                                                                      
+                                                 {
                                                                      
+                                                   'attrs' => [],
                                                                      
+                                                   'elems' => [
                                                                      
+                                                                bless
+( {
                                                                      
+                                                                     
+    'struct' => [... ],
                                                                      
+                                                                     
+    'elems' => [
                                                                      
+                                                                     
+                 {
                                                                      
+                                                                     
+                   ...                                               
+                                                                     
+ },
                                                                      
+                                                                     
+                 {
                                                                      
+                                                                     
+                   ...
                                                                      
+                                                                     
+                 },
                                                                      
+                                                                     
+                 {
                                                                      
+                                                                     
+                   ...
                                                                      
+                                                                     
+                 },
                                                                      
+                                                                     
+                 {
                                                                      
+                                                                     
+                  ...
                                                                      
+                                                                     
+                 },
                                                                      
+                                                                     
+                 {
                                                                      
+                                                                     
+                  ...
               }
                                                                      
+                                                                     
+               ],
                                                                      
+                                                                     
+    'tag' => 'sequence'
                                                                      
+                                                                     
+  }, 'BLOCK' )
                                                                      
+                                                              ],
                                                                      
+                                                   
                                                                      
+                                                 },
                                                                      
+                                                 {
                                                                      
+                                                   'attrs' => [],
                                                                      
+                                                   'elems' => [
                                                                      
+                                                                bless
+( {
                                                                      
+                                                                     
+    'struct' => [...],
                                                                      
+                                                                     
+    'elems' => [
                                                                      
+                                                                     
+                 {
                ...                                                   
+                                                         },
                                                                      
+                                                                     
+                 {
                                                                      
+                                                                     
+                   'attrs' => [],
                                                                      
+                                                                     
+                   'elems' => [
                                                                      
+                                                                     
+                                bless( {
                                                                      
+                                                                     
+                                         'struct' => [...            
+                                                                     
+                                                          ],
                                                                      
+                                                                     
+                                         'elems' => [
                                                                      
+                                                                     
+                                                      {...},
                                                                      
+                                                                     
+                                                      {...},
                                                                      
+                                                                     
+                                                      {
                                                                      
+                                                                     
+                                                        ...          
+                                          },
                                                                      
+                                                                     
+                                                      {
                                                                      
+                                                                     
+                                                       ...           
+                                                                     
+                                              },
                                                                      
+                                                                     
+                                                      {
                                                                      
+                                                                     
+                                                        ...
                                                                      
+                                                                     
+                                                      }
                                                                      
+                                                                     
+                                                    ],
                                                                      
+                                                                     
+                                         'tag' => 'sequence'
                                                                      
+                                                                     
+                                       }, 'BLOCK' )
                                                                      
+                                                                     
+                              ],
                                                                      
+                                                                     
+                   ...
                                                                      
+                                                                     
+                 }
                                                                      
+                                                                     
+               ],
                                                                      
+                                                                     
+    'tag' => 'sequence'
                                                                      
+                                                                     
+  }, 'BLOCK' )
                                                                      
+                                                              ],
                                                                      
+                                                   ...
                                                                      
+                                                 },
                                                                      
+                                                 {
                                                                      
+                                                   ...
                                                                      
+                                                 },
                                                                      
+                                                 {
                                                                      
+                                                   ...
                                                                      
+                                                 },
                                                                      
+                                                 {
                                                                      
+                                                   'attrs' => [],
                                                                      
+                                                   'elems' => [
                                                                      
+                                                                bless
+( {
                                                                      
+                                                                     
+    'struct' => [...],
                                                                      
+                                                                     
+    'elems' => [
                                                                      
+                                                                     
+                 {
                                                                      
+                                                                     
+                   'attrs' => [],
                                                                      
+                                                                     
+                   'elems' => [
                                                                      
+                                                                     
+                                bless( {
                                                                      
+                                                                     
+                                         'struct' => [...],
                                                                      
+                                                                     
+                                         'elems' => [
                                                                      
+                                                                     
+                                                      { ...},
                                                                      
+                                                                     
+                                                      {...},
                                                                      
+                                                                     
+                                                      {...}
                                                                      
+                                                                     
+                                                    ],
                                                                      
+                                                                     
+                                         'tag' => 'sequence'
                                                                      
+                                                                     
+                                       }, 'BLOCK' )
                                                                      
+                                                                     
+                              ],
                                                                      
+                                                                     
+                  ...                                                
+                                                          }
                                                                      
+                                                                     
+               ],
                                                                      
+                                                                     
+    'tag' => 'sequence'
                                                                      
+                                                                     
+  }, 'BLOCK' )
                                                                      
+                                                              ],
                                                                      
+                                                   ...
                                                                      
+                                                 },
                                                                      
+                                                 {
                                                                      
+                                                   ...
                                                                      
+                                                 },
                                                                      
+                                                 {
                                                                      
+                                                   ...
                                                                      
+                                                 }
                                                                      
+                                               ],
                                                                      
+                                    'tag' => 'sequence'
                                                                      
+                                  }, 'BLOCK' )
                                                                      
+                         ],
                                                                      
+              ...
                                                                      
+            },
                                                                      
+            {
                                                                      
+              'attrs' => [],
                                                                      
+              'elems' => [
                                                                      
+                           bless( {
                                                                      
+                                    'struct' => [...],
                                                                      
+                                    'elems' => [
                                                                      
+                                                 {...},
                                                                      
+                                                 {...},
                                                                      
+                                                 {...},
                                                                      
+                                                 {...},
                                                                      
+                                                 {...},
                                                                      
+                                                 {...},
                                                                      
+                                                 {...}
                                                                      
+                                               ],
                                                                      
+                                    'tag' => 'sequence'
                                                                      
+                                  }, 'BLOCK' )
                                                                      
+                         ],
                                                                      
+              ...
                                                                      
+            },
                                                                      
+            {
                                                                      
+              'attrs' => [],
                                                                      
+              'elems' => [
                                                                      
+                           bless( {
                                                                      
+                                    'struct' => [...],
                                                                      
+                                    'elems' => [
                                                                      
+                                                 {...},
                                                                      
+                                                 {...},
                                                                      
+                                                 {...},
                                                                      
+                                                 {...},
                                                                      
+                                                 {
                                                                      
+                                                   'attrs' => [],
                                                                      
+                                                   'elems' => [
                                                                      
+                                                                bless
+( {
                                                                      
+                                                                     
+    'struct' => [...],
                                                                      
+                                                                     
+    'elems' => [
                                                                      
+                                                                     
+                 {
                                                                      
+                                                                     
+                   'attrs' => [],
                                                                      
+                                                                     
+                   'elems' => [
                                                                      
+                                                                     
+                                bless( {
                                                                      
+                                                                     
+                                         'struct' => [...],
                                                                      
+                                                                     
+                                         'elems' => [
                                                                      
+                                                                     
+                                                      {...},
                                                                      
+                                                                     
+                                                      {...}
                                                                      
+                                                                     
+                                                    ],
                                                                      
+                                                                     
+                                         'tag' => 'sequence'
                                                                      
+                                                                     
+                                       }, 'BLOCK' )
                                                                      
+                                                                     
+                              ],
                                                                      
+                                                                     
+                  ...
                                                                      
+                                                                     
+                 }
                                                                      
+                                                                     
+               ],
                                                                      
+                                                                     
+    'tag' => 'sequence'
                                                                      
+                                                                     
+  }, 'BLOCK' )
                                                                      
+                                                              ],
                                                                      
+                                                  ...
                                                                      
+                                                 }
                                                                      
+                                               ],
                                                                      
+                                    'tag' => 'sequence'
                                                                      
+                                  }, 'BLOCK' )
                                                                      
+                         ],
                                                                      
+             ...
                                                                      
+            }
                                                                      
+          ],
                                                                     '
+tag' => 'sequence'
                                                                   }, 
+'BLOCK' )
                                                          ],
                                              ...
                                             },
                                             {
                                               'attrs' => [],
                                               'elems' => [
                                                            bless( {
                                                                     '
+struct' => [...],
                                                                     '
+elems' => [
                                                                      
+            {
                                                                      
+              'attrs' => [],
                                                                      
+              'elems' => [
                                                                      
+                           bless( {
                                                                      
+                                    'struct' => [...],
                                                                      
+                                    'elems' => [
                                                                      
+                                                 {...},
                                                                      
+                                                 {...},
                                                                      
+                                                 {...},
                                                                      
+                                                 {...}
                                                                      
+                                               ],
                                                                      
+                                    'tag' => 'sequence'
                                                                      
+                                  }, 'BLOCK' )
                                                                      
+                         ],
                                                                      
+              ...
                                                                      
+            }
                                                                      
+          ],
                                                                     '
+tag' => 'sequence'
                                                                   }, 
+'BLOCK' )
                                                          ],
                                               ...
                                             }
                                           ],
                                'tag' => 'sequence'
                              }, 'BLOCK' )
                     ],
         ...
        };
[download]

QUESTION: I've never seen bless used in this context and definitely never nested like this. The concept of bless is still a little obscure to me. I guess I learn the best from example code. Since I haven't found any yet used in this way, I'm completely stumped as to why bless was used and what is the best way to access these elements? I'm able to drill down the structure just like it's a typical HOA, but why bless? I'm assuming bless is doing something special here, but I can't figure it out. Can someone shed some light for me?

UPDATED: original post was cut off for being too long. Abbreviated LOG output.

Comment on Nested Bless within Hash of Arrays Select or Download Code

Replies are listed 'Best First'.
Re: Nested Bless within Hash of Arrays by chromatic (Archbishop) on Jul 22, 2013 at 21:31 UTC
I'm able to drill down the structure just like it's a typical HOA, but why bless? bless associates the name of a package with a reference. It's ultimately how you create new object instances in Perl 5 right now. You're seeing a textual serialization of your objects and how to thaw them. Improve your skills with Modern Perl: the free book.	[reply]
Re^2: Nested Bless within Hash of Arrays by ksublondie (Friar) on Jul 22, 2013 at 22:05 UTC
As in `BLOCK = $t->{elems}->[0]`? But then what is `$t->{elems}->[0]->{elems}->[1]->{elems}->[0]` since it's also blessed as BLOCK?	[reply] [d/l] [select]
Re^3: Nested Bless within Hash of Arrays by chromatic (Archbishop) on Jul 23, 2013 at 00:08 UTC
It's another instance of `BLOCK`, as in `my $something = BLOCK->new( { ... } );`, but without the intermediary `$something`.	[reply] [d/l] [select]
Re: Nested Bless within Hash of Arrays by Loops (Curate) on Jul 22, 2013 at 20:46 UTC
Was there a question in there somewhere? Update: Ah yeah, figured something like that happened. You might want to take a quick peek at bless and some of the documents it references.	[reply]
Re^2: Nested Bless within Hash of Arrays by ksublondie (Friar) on Jul 22, 2013 at 21:14 UTC
I'm sorry, but there are no documents referenced nor is there any useful information in that post. Perhaps you meant to post some other link??? I've been reading as much as I can find regarding `bless`, but haven't found it used in this way or any examples WITHIN hashes.	[reply] [d/l]
Re^2: Nested Bless within Hash of Arrays by ksublondie (Friar) on Jul 22, 2013 at 20:58 UTC
Updated OP. The post preview didn't give me any indication that it was too long and cut off. It let me create, view, and edit the post in entirety. Only when I went back into the post from another route did I see it was cut off.	[reply]
Re^2: Nested Bless within Hash of Arrays by ksublondie (Friar) on Jul 22, 2013 at 21:28 UTC
Thanks for fixing the link. I've read all that before, but since it doesn't talk about or give any examples of any blessings INSIDE a hash, I'm missing something.	[reply]
Re: Nested Bless within Hash of Arrays by hdb (Monsignor) on Jul 23, 2013 at 07:17 UTC
In Data::Dumper's output, `bless` signifies a blessed reference. Have a look at this example: `use strict; use warnings; use DateTime; use Data::Dumper; my $t = DateTime->now; print Dumper $t;` [download] which creates this output: $VAR1 = bless( { 'local_rd_secs' => 25639, 'local_rd_days' => 735072, 'rd_nanosecs' => 0, 'locale' => bless( { 'default_time_format_length' => +'medium', 'native_territory' => 'United St +ates', 'native_language' => 'English', 'native_complete_name' => 'Engli +sh United States', 'en_language' => 'English', 'id' => 'en_US', 'default_date_format_length' => +'medium', 'en_complete_name' => 'English U +nited States', 'en_territory' => 'United States +' }, 'DateTime::Locale::en_US' ), 'local_c' => { 'hour' => 7, 'second' => 19, 'month' => 7, 'quarter' => 3, 'day_of_year' => 204, 'day_of_quarter' => 23, 'minute' => 7, 'day' => 23, 'day_of_week' => 2, 'year' => 2013 }, 'utc_rd_secs' => 25639, 'formatter' => undef, 'tz' => bless( { 'name' => 'UTC' }, 'DateTime::TimeZone::UTC' ), 'utc_year' => 2014, 'utc_rd_days' => 735072, 'offset_modifier' => 0 }, 'DateTime' ); [download] This tells you that `$t` is a blessed hash reference with classname `DateTime`. The hash itself contains all the members of the class some of which again are blessed hash references (like `locale` and `tz`) of different types (classes). In the structure you have posted, it seems that the class `BLOCK` has elements that are blocks themselves, like `BLOCK`s of `BLOCK`s. In a way this is not much different from arrays of arrays.	[reply] [d/l] [select]
Re^2: Nested Bless within Hash of Arrays by ksublondie (Friar) on Jul 23, 2013 at 15:49 UTC
Ok, so the "blessing" is just a specification by Dumper that the element is a `BLOCK` object?	[reply] [d/l]
Re^3: Nested Bless within Hash of Arrays by hdb (Monsignor) on Jul 23, 2013 at 15:51 UTC
It is to tell you that the reference provided to Dumper has been blessed as a BLOCK.	[reply] [d/l]