END blocks are executed in the reverse order they are encountered. So if you put an END block right at the top of your program that sets $?, you should be set.

my $rv = 2;  # assume fatal.
END { $? = $rv; }

use ...
use ...

{
   ...

   if (...) { $rv = 1; exit(); }

   ...
   
   $rv = 0;
}
[download]