Found it out myself:

Actually

package App;
sub new{
  ## > here IS RIGHT!
}
1;
[download]

you just have to make sure that you do not access things (for example TextCtrls) that haven't been created. As most of this stuff is established in this new() routine, make sure to place your has_expired()-like routines at the end of new() after all you are working with is actually there...