I doubt if it got corrupted by the installation process; it's a pure perl module so should be pretty straight forward.

I'm working on a Windows machine w/Active perl at the moment and was moderately surprised to find there don't seem to be any ppm packages for that module generally available.

Ah well, I went ahead and installed it manually and tried (a suitably modified version of) your script and am getting the same results locally.

In poking around a bit, it looks to me like a bug in Net::FTP::Find::Mixin. Specifically, in line 116:

if ($depth == 0) {
    next if $_ ne '.'; # <-- line 116
    $_ = $directory;
}
[download]

The logic seems backwards; I believe it should be eq not ne.

if ($depth == 0) {
    next if $_ eq '.';
    $_ = $directory;
}
[download]

With that change made locally it works as I would expect... And on inspection of the Net::FTP::Find::Mixin CPAN page, there is an open bug report filed about this very problem, (Though it doesn't mention the above solution)