#!/usr/bin/perl

use strict; # https://perlmonks.org/?node_id=11126426
use warnings;

my $str = join '', map '.' x $_ . "this is line $_\n", 1 .. 60;
print $str;
print "string length = ", length $str, "\n";

my $backwards = Tybalt89BackwardsHeReads->new( \$str ) or die;

while( defined( $_ = $backwards->line ) )
  {
  print;
  }

package Tybalt89BackwardsHeReads; #######################################

sub line
  {
  my ($self) = @_;
  if( @{ $self->{lines} } == 0 and $self->{where} )
    {
    my $window = 1024;                   # window size, adjust to suit
    my $pos = $self->{where} - $window;
    $pos < 0 and $pos = 0;
    seek $self->{fh}, $pos, 0;
    read $self->{fh}, my $data, $self->{where} - $pos;
    $pos and $data =~ s/^.*\n// ? ($pos += $+[0]) : die "increase window size";
    $self->{lines} = [ split /^/, $data ];
    $self->{where} = $pos;
    }
  return pop @{ $self->{lines} };
  }

sub new
  {
  my ($self, $filename) = @_;
  open my $fh, '<', $filename or die "$! on $filename";
  bless { fh => $fh,
    where => ref $filename ? length $$filename : -s $filename,
    lines => [] }, ref $self || $self;
  }

1; # so if split off, package ends with true