Variables

    my $delivery = $iter -> next();
    
    #-----------------------------------------
    #  Sender, ReceiverList, Size, and Date are the most useful
    #-----------------------------------------
    
    # e-mail address of sender, may be 'undef' if the sender
    # could not be determined from the syslog
    my $sender = $$delivery{Sender};
    
    # reference to array of e-mail addresses of recipients
    my $paReceiverList = $$delivery{ReceiverList};
    my @aReceiverList = @$paReceiverList;
    print "The recipient(s) of the message was (were) ",
        join(' ',@aReceiverList), "\n";
    
    # size of message, may be 'undef' if the size could not be
    # determined from the syslog
    my $sizeInBytes = $$delivery{Size};
    
    # date the message was succesfully delivered or forwarded
    my $date = $$delivery{Date};
    
    #-----------------------------------------
    #    Id and Instance are more advanced features
    #-----------------------------------------
    
    # 'id' in syslog, useful for cross-referencing
    my $id = $$delivery{Id};
    
    # The first delivery of any message has Instance of 1; the next
    # deliveries will have Instance > 1, specifically a number equal to
    # the number of people who the message has previously been delivered
    # to, plus 1.  This is useful for detecing mass-mailings.
    
    # Suppose I send a message to 5 people, but only three copies are
    # delivered right away, the other two are deferred.  The first
    # Delivery has instance 1; the next delivery of the same message
    # will have instance 4.
    my $instance = $$delivery{Instance};
    my @aReceiverList = @{$$delivery{ReceiverList}};
    print "This message has so far been delivered to ",
        $instance + $@aReceiverList - 1, "people so far\n";