If you really have version 1.31 then you are running a 15 year old version. In this case you should no longer wonder about problems but upgrade your system. But, a version of 1.31 never occurs in the ChangeLog of IO::Socket::INET6, i.e. it goes straight from 1.28 to 2.00. How did you determine the version of IO::Socket::INET6 (which is not the same as IO::Socket!)?