I was able to remove the error by deleting the par unzipping directories in /tmp/par*.

I wonder if that will work for all situations ?

I can remember PAR playing the same trick a few years back - it was a different module involved (Compress::Zlib, I think), but the same annoying trick. I forget the precise circumstances. Did you build PAR itself ? or did you install a pre-compiled version that was built for your platform ? (My vague recollection is that the original problem to which I refer applied to the latter case.)

I would probably try to address this particular issue wrt Set::Object by first ascertaining the version of Set::Object that's installed. Then, if it's 1.22, I'd install 1.21 ... or if it's 1.21, I'd install 1.22.

But, in any case, it's a bug - and you could consider reporting it. At a quick glance, it doesn't appear to have been reported to rt.cpan.org, so you could report it there, or just raise it on the PAR mailing list if you prefer.

Cheers,
Rob