This is fine if you just need it to sleep for around 15 seconds. If you need it to sleep for "exactly" 15 seconds, you will probably want to use Time::HiRes and usleep, and do the elapsed time tracking yourself so you can be sure to get all the sleep you need.

Remember, sleep does not sleep for the exact duration you tell it. It only sleeps for that many wall clock ticks and that could include a fraction of a whole second. Sleep for 1 fractional second 15 times and you could get much less sleep than you need.