How Do You Tell Time in Perl?

I need to write a couple of Perl scripts that operate on a cache, and
the page replacement policy for this cache is Least Recently Used,
which means I need to record a time value for each entry in the cache.
How can one tell what the time is in Perl, so that each time I access
one of these entries I can modify its timestamp? Any information on
this would be greatly appreciated.

I know that I can find out how Perl works with the "perldoc" command,
but that command expects a module name as an argument, and I have no
idea which module has to do with telling time.

---Kevin Simonson

"You'll never get to heaven, or even to LA,
if you don't believe there's a way."
from _Why Not_