Current Perl documentation can be found at perldoc.perl.org.

Here is our local, out-dated (pre-5.6) version:

If you want finer granularity than the 1 second that the sleep() function provides, the easiest way is to use the select() function as documented in select. If your system has itimers and syscall() support, you can check out the old example in http://www.perl.com/CPAN/doc/misc/ancient/tutorial/eg/itimers.pl .