Time::HiRes does not export routines with the names gettimer or settimer . Please take care to spell the functions with the same name as they use in the documentation. The names used there are getitimer and setitimer, the additional "i" standing for "interval". It helps people unfamiliar with the functions you mention if you link to the documentation, and of course it helps them even more if you give them the correct word to seach in the page.