my $exit;
local $SIG{INT} =
local $SIG{TERM} = sub { $exit = 1; };

my $wakeup_time = time + 60*60;
for (;;) {
   if ($exit) {
      ...
      exit(0);
   }

   my $sleep_dur = $wakeup_time - time;
   last if $sleep_dur <= 0;
   sleep($sleep_dur);
}