Returns the number of non-leap seconds since whatever time the system
considers to be the epoch, suitable for feeding to gmtime and
localtime. On most systems the epoch is 00:00:00 UTC, January 1, 1970;
a prominent exception being Mac OS Classic which uses 00:00:00, January 1,
1904 in the current local time zone for its epoch.
For measuring time in better granularity than one second,
you may use either the Time::HiRes module (from CPAN, and starting from
Perl 5.8 part of the standard distribution), or if you have
gettimeofday(2), you may be able to use the syscall interface of Perl.
See perlfaq8 for details.
For date and time processing look at the many related modules on CPAN. For a comprehensive date and time representation look at the DateTime module.