Is this a bug with IO::Uncompress::AnyUncompress?

Maybe (probably not) , maybe its a problem with the any being used :) do you have the latest version ( PMQS/IO-Compress-2.062.tar.gz )?

maybe its a problem with the file.

Is this something wrong with my code that attempts to use IO::Uncompress::AnyUncompress?

Probably not (looks like its following docs).