[mh] Throttle Email Messages

[John <jo...@to...>]

What is the misterhouse pattern to throttle something like sending 
emails?  I have a timer that once every 20 minutes triggers an action.  
In that action I am sending an email.  For example:

my $object = &::get_object_by_name('mechroom_water_detector');
$object->manage_heartbeat_timeout($xpl_timeout, \&report_xpl_offline, -1);

sub report_xpl_offline {
     net_mail_send(to => 'my...@bl...v', subject => 'ALERT: Water 
detector is not online', text => 'AL
ERT: Water detector is not online');

     print_log "Water Detector is OFFLINE";

}

I want to send that email at most once per day (for example).  I am OK 
with case where sensor comes online and back offline in the same day (OK 
with only one email going out).

One option was to save the time last email was sent and have logic based 
on that.  I was just thinking there may be a construct for this kind of 
thing.

John