To get high resolution sleep intervals on a Unix system, try Time::HiRes or BSD::Itimer, depending on your OS. To use Time::HiRes to sleep for an interval:

use Time::HiRes qw( usleep );

usleep ($microseconds);
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Assuming Time::HiRes installs properly, you will get a highly accurate sleep interval. But latency and timing jitter depend on more than this. In a pre-emptive multitasking system with other processes running, it is very hard to predict when, say, Csound will read your command and start generating sound. I have seen jitters of up to 10 msec on my Linux machine. If you need low jitter, I would recommend dumping as many unneeded processes as possible and setting your desired processes to high priority.

Even better is to have realtime control of your OS. Check out RTLinux for an elegant realtime version of the Linux kernel.

-Mark