Thank you, it seems you have found the source of the problem.

The .pm version of Params::Classify the docs are talking about is right beside the .xs module in the source archive.

If I edit the .pm module and comment-out the lines:

eval { local $SIG{__DIE__};
    require XSLoader;
    XSLoader::load(__PACKAGE__, $VERSION);
};
[download]

everything works correctly.