phpman > perldoc > SLEEP(10)

Found in /usr/share/perl/5.34/pod/perlfaq8.pod
  How can I sleep() or alarm() for under a second?
    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" in perlfunc. Try the Time::HiRes and the
    BSD::Itimer modules (available from CPAN, and starting from Perl 5.8
    Time::HiRes is part of the standard distribution).