Most of the functions would be in VICommon.pm.  You'll find several regexp in the module that parse the host portion of the URI as an IPv4 address.  There might other places to modify, bu that I think those are the core (assuming support for IPv6).  You may also need to pull out the hard-coded Crypt::SSLeay module imports to favor IO::Socket::SSL.  As others have pointed out, Crypt::SSLeay is more of a legacy play (it doesn't support robust certificate validation, so it's a possible weakness to Man-In-The-Middle).

Are you really limited to IPv6 for the vCenter connectivity?  Perhaps an Ipv6 proxy might be a solution?