#!/usr/bin/perl

use strict;
use warnings;
use Data::Dumper;

my $head = {data => 0, prev => undef, next => undef};
my $previous = $head;

open FILE, "<datastored.txt" or die $!;

while (<FILE>){
    chomp;
    $previous->{next} = {
                "data" => $_ ,
                "next" => undef,
                "prev" => $previous,
            };
    $previous = $previous->{next};

}

### Inserting element after the head node
my $curr = $head;
$curr->{next}= {
                 "data" => 30, 
                "next" => $curr->{next},
                "prev" => $curr,
};

$curr->{next}{next}{prev}=$curr->{next};

#
# Inserting element before the tail node
 $curr = $previous;
 $curr->{prev}= {
                 "data" => 40, 
                "next" => $curr,
                "prev" => $curr->{prev},
};

$curr->{prev}{prev}{next}=$curr->{prev};

## Printing from head
print "printing from head \n";

print Dumper($head);


 $curr = $head;
while (1) {
    last unless defined $curr->{next};
    print "Current: ", $curr->{data},
          "\tPrevious: ", $curr->{prev}{data} // "",
          "\tNext: ", $curr->{next}{data} // "", "\n";
    $curr = $curr->{next};
}


## printing from tail


print "\n Printing From tail \n";

while (1) {
    last unless defined $curr->{prev};
    print "Current: ", $curr->{data}, 
          "\tPrevious: ", $curr->{prev}{data} // "",
          "\tNext: ", $curr->{next}{data} // "", "\n";
    $curr = $curr->{prev};
}


##</code><code>##


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


##</code><code>##

line1
line2
line3
line4