I have found a problem with Time::HiRes under Cygwin. Seems that the Time::HiRes::time() function slowly falls behind Perl's core time() function. Running the following for an hour or so illustrates this on my PC, especially when it is under load. 
#!/usr/bin/perl

use strict;
use warnings;

use Time::HiRes;

while (1) {
    print("Core : ", scalar localtime(), "\n");
    print("HiRes: ", scalar localtime(Time::HiRes::time), "\n\n");
    sleep(60);
}

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Update:I found the source of the problem.

PCs are terrible time keepers. It seems that under heavy load, the clock can continually loose time. On my laptop, I run an NTP client every 5 minutes to compensate for this. Doing so then causes problems with Time::HiRes. Whereas Perl's core time() function picks up on the NTP clock adjustments, Time::HiRes::time() does not.

You can see this by running the script above with sleep(10). Then adjust your PC's clock. You'll see that the 'Core' time picks up the adjustment, but the HiRes time does not.

Whether this constitutes a bug in Time::HiRes or not is a question.

In reply to Time::HiRes::time() Bug on Cygwin by jdhedden

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