This is interesting!

If you're importing subs, you must also replace them in the importing package. It's best to call import() on the reloaded package specifically. Observe:

use QStat;
foo();
print "QStat foo is: ", \&QStat::foo, "\n";
print "Imported foo is: ", \&main::foo, "\n";

<STDIN>;

my $loc = $INC{QStat};
delete $INC{QStat};
require $loc;

# slightly more difficult
# QStat->import();

print "After import, foo is: ", \&main::foo, "\n";
print "And in the package it is: ", \&QStat::foo, "\n";
[download]

Try it with and without the import(), and you'll see what's going on. *foo in the main package and *foo in QStat will point to different CVs, and that's the problem. (The STDIN part is in there so I could change what foo() does while the program is running.)

I wonder if it would be worth writing a 'reimport' module...