#!/usr/bin/perl -w

use strict;

# we're abusing signals for this trick
$SIG{ALRM} = \&wake_up;
start();

sub start {
	# arbitrary number, could be a variable
	alarm(5);
	while (1) {
		# random time so the handler executes in different spots
		sleep int rand(3);
		print "Here's a line after a sleep.\n";
		sleep int rand(3);
		print "Here's a line after another sleep.\n";
		
		# don't interrupt this chunk
		my $hold = alarm(0);
		print "Suspending alarm with $hold second(s) left.\n";
		sleep int rand(3);
		print "There should never be an alarm right before this.\n";
		
		# interruptions okay now
		alarm($hold);
		sleep int rand(3);
		print "This is the last line of the loop.\n\n";
	}
}

sub wake_up {
	# don't interrupt the interrupt (probably unnecessary)
	$SIG{ALRM} = 'ignore';
	print "\t=> in alarm handler <=\n";
	# reset alarm
	alarm(5);
	# reinstall handler
	$SIG{ALRM} = \&wake_up;
}