This variable is global in scope and is used to hold a DS map when used in the IAP Event, and -1 at all other times. The actual contents of the DS map will depend on the type of event that was used to trigger it, so refer to the IAP Event pages for more details.
Real (integer value)
if iap_data[? "type"] == iap_ev_storeload
global.iap_enabled = true;
else global.iap_enabled = false;
The above code is taken from the Image Loaded Asynchrnous Event and will first check the ID of the async_load DS map that has been populated, then check the status of the callback. If the value is greater than or equal to 0 (signalling success) the result from the callback will then be used to set the background index to the newly loaded image.