I read this code sample and interpret as following. You are trying to retrieve the collection of appointments in outlook. However what you seem to be doing is creating a single appointment in

my $app = $namespace->CreateItem(olAppointmentItem);
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and trying to retrieve the Items collection of the Appointment. Perl is telling you that there is no Items collection attached to an Appointment Item.

Look at your first question and try something allong the lines of:

1. Retrieve the Namespace
2. Get the DefaultFolder that contains Calendar objects.
3. Retrieve collection of appointments
4. With the collcation add an appointment.