#!/usr/bin/perl

use strict;
use warnings;

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

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

my $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};
}

__DATA__
1
2
3
4
5

##</code><code>##

$ perl  doubly_linked.pl
Current: 0      Previous:       Next: 1
Current: 1      Previous: 0     Next: 2
Current: 2      Previous: 1     Next: 3
Current: 3      Previous: 2     Next: 4
Current: 4      Previous: 3     Next: 5

##</code><code>##

$VAR1 = {
          'next' => {
                      'next' => {
                                  'next' => {
                                              'next' => {
                                                          'next' => {
                                                                      'next' => undef,
                                                                      'prev' => $VAR1->{'next'}{'next'}{'next'}{'next'},
                                                                      'data' => '5'
                                                                    },
                                                          'prev' => $VAR1->{'next'}{'next'}{'next'},
                                                          'data' => '4'
                                                        },
                                              'prev' => $VAR1->{'next'}{'next'},
                                              'data' => '3'
                                            },
                                  'prev' => $VAR1->{'next'},
                                  'data' => '2'
                                },
                      'prev' => $VAR1,
                      'data' => '1'
                    },
          'prev' => undef,
          'data' => 0
        };