Maybe someone could be a real chum and write a ++/-- overload system that would allow you to add and subtract times? Date::Calc is great and all, but something more low level could come in handy now and then. Like a Date type with a full suite of arithmetic overloads.

As for me, I prefer to use the UNIX time_t type times, which are 9/10 digit numbers and can represent an exact date and time, not just time. To iterate through them you could do something like:

use Time::Local;

for (timelocal(0,0,0,1,0,100)..timelocal(59,59,23,1,0,100))
{
     my ($s,$m,$h) = localtime($_);
}
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That will go through the first day of January (month #0) of 2000 (year 1900+100), second by second. I'm using localtime to extract the HH:MM:SS data.