#! perl
use strict;
use warnings;

use constant
{
    DELAY  =>   10,
    EXPIRY => 3600,
    MARGIN =>  300,
};

my $time   =  time;
my $expiry = $time + EXPIRY;

while ($time + MARGIN < $expiry)
{
    my $previoustime = $time;
    warn $time;

    sleep DELAY + $previoustime - $time
        unless $time - $previoustime >= DELAY;

    $time = time;
}