I doubt it. Here are the results of several runs: 
[snowhare]$ ./hires-time.pl
1133389582245150
1133389582245151
[snowhare]$ ./hires-time.pl
113338958348908
113338958348909
[snowhare]$ ./hires-time.pl
1133389583585585
1133389583585586
[snowhare]$ ./hires-time.pl
1133389584217773
1133389584217774
[snowhare]$ ./hires-time.pl
1133389584827558
1133389584827559
[snowhare]$ ./hires-time.pl
1133389585762938
1133389585762939
[snowhare]$ ./hires-time.pl
1133389586273604
1133389586273605
[snowhare]$ ./hires-time.pl
1133389586920152
1133389586920152
[snowhare]$ ./hires-time.pl
1133389587601760
1133389587601761

[download]

If it was simply being cached, I would expect it to always give me 0 microsecond results - instead I get it perhaps one time in eight (which makes sense since the machine is doing a number of other things as well so I don't expect 100% repeatability in the runs' timing).

Unless you can spot something in Time::HiRes itself that would cause caching, I am inclined to view the numbers as correct. Regardless, it shows that Time::HiRes can produce identical timestamps when pushed hard on a fast machine (in this case a Linux box running perl 5.6.2.)

In reply to Re^4: OT How fast a cpu to overwhelm Time::HiRes by snowhare
in thread OT How fast a cpu to overwhelm Time::HiRes by zentara

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