use threads;
use threads::shared;

my ($global):shared;

my $handler=threads->create(\&handler)->detach;

do
	{
	
	print "Enter a value for shared global variable ( x = exit ): ";chomp($global=<>);
	
	sleep(3);
	
	} while($global ne 'x');

sub handler
{

my $global_old=$global;

while(1)
	{

	if($global ne $global_old)
		{
		
		print "User changed the global variable to '$global'.\n";
		$global_old=$global;
		
		}

	sleep(1);

	}

}