use ExtUtils::Installed;
my ($inst) = ExtUtils::Installed->new();
print grep /auto/, $inst->directories("Acrobat::FDF");
[download]

On my machine, and most default installs, all *.dll's should should go under $Config{sitearch}/auto/Distribution/Name, so Distrubution-Name can find it, or $Config{scriptdir}, so every perl module can find it.

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