#!/usr/bin/perl

use strict;
use warnings;

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 at the beginning of the list after the head node
my $curr = $head;
$curr->{next}= {
                 "data" => 30, 
                "next" => $curr->{next},
                "prev" => $curr,    
};


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


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

 $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 "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>##


printing from head 
Current: 0	Previous: 	Next: 30
Current: 30	Previous: 0	Next: line1
Current: line1	Previous: 0	Next: line2
Current: line2	Previous: line1	Next: line3
Current: line3	Previous: line2	Next: line4
Current: line4	Previous: line3	Next: line5


Printing From tail 
Current: line5	Previous: 40	Next: 
Current: 40	Previous: line4	Next: line5
Current: line4	Previous: line3	Next: line5
Current: line3	Previous: line2	Next: line4
Current: line2	Previous: line1	Next: line3
Current: line1	Previous: 0	Next: line2
Current: 0	Previous: 	Next: 30


##</code><code>##

line1
line2
line3
line4
line5