Perl isn't the right tool for this job, go find xntpd and use it. At the very least get ntpdate from the same package and stick it in your crontab.

Doing NTP right for system timesync requires exacting maths and tight OS integration. Also, once you have xntpd running on your server, you can use it as a clean time source for all the other computers in your network. Dimension4 works great if you are stuck with M$PCs and need to timesync them to your Linux box.

--
$you = new YOU;
honk() if $you->love(perl)