> This would not fulfil the requirement that at most three service calls must be done. > For doing this, you also have to monitor the time (though you don't have to do it > using a timer). It does fulfill the requirements. It does monitor the time.

Right, I should have looked more carefully.

For this particular example, install it

I think I should have been more precise. When talking about when a busy loop might be more appropriate than using the HiRes timer, I meant that we might be on a system where HiRes would not work. From the perldoc of HiRes: The "Time::HiRes" module implements a Perl interface to the "usleep", "nanosleep", "ualarm", "gettimeofday", and "setitimer"/"getitimer" system calls, so I think this means you need at least a platform having these system calls.

Note that I'm not against using Timer::HiRes. I just wanted to point out to the OP that if he doesn't WANT to use a sleep, he could alternatively do it using a busy loop.