title: "callback" from PayPal to confirm payment?
body: <p>I have a very simple online ordering app in Perl.  The user fills in a form, and when they submit, my app inserts the info into a mySql database, then redirects them to PayPal to complete the payment.  The problem is that the database does not have any information about whether they actually completed the payment.  I end up having to manually reconcile a report from PayPal with my database to confirm payment for each order.</p>
  
  <p>Is there anything like a "callback" from PayPal, where I could provide PayPal with a unique identifier for the order and PayPal could send back that identifier as confirmation that the order was paid, preferably through an HTTP request back to my server?  Then I could update the order in my database with a "paid" flag.</p>