#!/usr/bin/perl
use strict;
use warnings;
use Tie::File;
use Tie::Watch;

$main::touched=0;
my @array;
my $file='test_tie_file';
sub touched {$main::touched=1}


push @array, int (rand 1000) until $#array > 39; # fill it on the first pass

my $watch = Tie::Watch->new(
     -variable => \@array,
     -debug    => 0,
     -shadow   => 1,
     -fetch    => sub {print "Fetch\n";   
	               my $self=shift; 
		       $self->Fetch},
     -store    => sub {print "Store\n";
	               $main::touched=1; 
		       my $self=shift; 
		       $self->Store (@_)},
     -push     => sub {print "Push\n";    
	               $main::touched=1; 
		       my $self=shift; 
		       $self->Push (@_)},
     -clear    => sub {print "Clear\n";   
	               $main::touched=1; 
		       my $self=shift; 
		       $self->Clear   (@_)},
     -extend   => sub {print "Extend\n";  
	               $main::touched=1; 
		       my $self=shift; 
		       $self->Extend  (@_)},
);

tie @array, 'Tie::File', $file or die "cannot tie to $file: $!\n";
$main::touched=0;
print "array of length $#array is now watched\n";

print "would you like to alter the file (y/n)\n";
my $ansa=<STDIN>;
push @array, 'touched' if $ansa =~/^y/;

untie @array;
$watch->Unwatch;

if ($main::touched) {
    print "File has been altered\n"
} else {
    print "File remains the same\n";
}