If your primary goal is to avoid drift, then this routine will do the trick (within the limitations of the system clock):

$|= 1; my $i; my $start_time = time; my $period = 60; while (1) { print time, "\n"; my $next_sleep = ($start_time + $period * ++$i) - time; sleep $next_sleep; } [download]

This guarantees that future samples won't compound the timming imprecisions of prior samples.

   MeowChow                                   
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