A Time::Clock object is a twenty-four hour clock with nanosecond
precision and wrap-around. It is a clock only; it has absolutely
no concept of dates. Vagaries of date/time such as leap seconds
and daylight savings time are unsupported.
When a Time::Clock object hits 23:59:59.999999999 and at least one
more nanosecond is added, it will wrap around to 00:00:00.000000000.
This works in reverse when time is subtracted.
Time::Clock objects automatically stringify to a user-definable
format.
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