#!/usr/bin/env perl

use strict;
use warnings;
use autodie qw{:all};

use Tie::File;

my $target_in =  './pm_1073422_test.txt';
my $target_out = './pm_1073422_test.out';

print "*** Using Disk File ***\n";
{
    open my $fh_out, '>', $target_out;
    emulate_ctx_cat($fh_out, $target_in);
    close $fh_out;

    system cat => $target_out;
    unlink $target_out;
}

print "*** Using Array ***\n";
{
    open my $fh_out, '+>', undef;
    emulate_ctx_cat($fh_out, $target_in);
    tie my @text, 'Tie::File', $fh_out;

    print "* Original Text *\n";
    print "$_\n" for @text;

    $text[2] = 'Modified line';
    print "* Modified Text *\n";
    print "$_\n" for @text;

    untie @text;
    close $fh_out;

    print "* Original File *\n";
    system cat => $target_in;
}

sub emulate_ctx_cat {
    my ($fh_out, $target) = @_;

    open my $fh_in, '<', $target;

    while (<$fh_in>) {
        print $fh_out $_;
    } 

    close $fh_in;
}