Benchmark: timing 5 iterations of FastMktime::caching_mktime, POSIX::mktime, TIME::Local::timegm_nocheck...
FastMktime::caching_mktime: 65 wallclock secs (64.77 usr +  0.02 sys = 64.79 CPU) @  0.08/s (n=5)
POSIX::mktime: 118 wallclock secs (58.16 usr + 60.47 sys = 118.63 CPU) @  0.04/s (n=5)
TIME::Local::timegm_nocheck: 143 wallclock secs (143.07 usr +  0.54 sys = 143.61 CPU) @  0.03/s (n=5)