punit:Desktop punitpawar$ perl test1.pl 
printing Dumper 
$VAR1 = {
          'data' => 0,
          'prev' => undef,
          'next' => {
                      'prev' => $VAR1,
                      'next' => {
                                  'next' => {
                                              'data' => 'line 2',
                                              'next' => {
                                                          'next' => {
                                                                      'prev' => $VAR1->{'next'}{'next'}{'next'}{'next'},
                                                                      'next' => {
                                                                                  'data' => 'line 4',
                                                                                  'next' => undef,
                                                                                  'prev' => $VAR1->{'next'}{'next'}{'next'}{'next'}{'next'}
                                                                                },
                                                                      'data' => 40
                                                                    },
                                                          'prev' => $VAR1->{'next'}{'next'}{'next'},
                                                          'data' => 'line 3'
                                                        },
                                              'prev' => $VAR1->{'next'}{'next'}
                                            },
                                  'prev' => $VAR1->{'next'},
                                  'data' => 'line 1'
                                },
                      'data' => 30
                    }
        };



 printing from head 
Current: 0	Previous: 	Next: 30
Current: 30	Previous: 0	Next: line 1
Current: line 1	Previous: 30	Next: line 2
Current: line 2	Previous: line 1	Next: line 3
Current: line 3	Previous: line 2	Next: 40
Current: 40	Previous: line 3	Next: line 4

 Printing From tail 
Current: line 4	Previous: 40	Next: 
Current: 40	Previous: line 3	Next: line 4
Current: line 3	Previous: line 2	Next: 40
Current: line 2	Previous: line 1	Next: line 3
Current: line 1	Previous: 30	Next: line 2
Current: 30	Previous: 0	Next: line 1
Current: 0	Previous: 	Next: 30