This is brilliant work. Firefox extension development suddenly became so much easier (especially for Perl people). Thank you for writing this.
It would be nice to have something like this in the base installation of Perl. That way, when I subclass Module::Build to have do extra actions upon install (like recursively copying a dir from one place to another), I would have a pure perl way of doing this portably without having to pull extra modules from CPAN. Currently, I've resorted to doing `system("cp -auv $src $dst")` which is fine for systems with GNU/cp, but not for anyone else. Maybe it's a bit too late for perl5 but for perl6, let's think about having a more complete set of file manipulation libs in the base.