Although it looks as though your problem has been solved, I have some unsolicited advice anyway. :-)

Before assuming that you are seeing a particular problem, it can be helpful to isolate it. That way when you ask questions about it you can be pretty positive that you are asking about a real issue.

For instance, you might have tried running perl -e "sleep 2 * 3600" and checking your CPU utilization. If it were high you would have been pretty sure that sleep() was indeed the cause of the problem and been able to post a minimal example reproducing the issue. Of course, in this case the utilization would not have been high indicating that the problem was not with sleep() at all. That might have prompted you to check your logic or ask a more appropriate question.

-sauoq
"My two cents aren't worth a dime.";