I read up on some of the documentation on END and I think the answer to your problem is pretty simple. According to perlmod: END {} blocks are executed in reverse order. The last END created is the first END that gets executed. It seems all you need to do is define your END {} at the very beginning of your program before the other ones get defined. That should allow you to set your $? variable to whatever you want since by the time its seen all of the modifications to it should have already happened.

use is really just a BEGIN {} block and BEGIN executes in the order its seen. You could create a module that has your final end block and use it the very first. Tell it to redefine $? to some other value. use all of your other modules then at the end of all that use another module that creates an END { } that saves the original exit value from the program. Something like this:

#!/usr/bin/perl
use strict;
use vars qw($myexitvalue);
use MyLastEnd;
use Foo;
use Bar;
use SomeOtherModule;
use MyFirstEnd;

# rest of script

#MyLastEnd.pm
END {
     $? = $myexitvalue;
}

#MyFirstEnd.pm
END {
    $myexitvalue = $?;
}
[download]

All of this is untested of course, but if I'm reading the docs right it *should* work. Hope that helps!