Unfortunately, when someone comes to me and says, "Your module produces errors or warnings on my ActivePerl install," it's difficult for me to determine that it's because a core module several layers up the chain is different. I certainly don't want to consult that patch file for every recursively included module. The changed rmtree didn't just address some vulnerability, it introduced at least one new behavior, carping on  as the first arg to rmtree. With a core that doesn't behave like the perl core, it's harder to support. The changes may be minor, but they're distracting and make debugging take significantly longer where it shouldn't, liked in pure Perl modules. As someone who tries to support every platform, I find it very frustrating.