When a datatype does not match any of the regular
expressions a generic serialization function is used to
serialize the data. Since the form of the data is not
know, it may contain various characters that require
escaping. This is definitely true of the anyURI support
as & characters need to be properly encoded.
I have attached a patch to fix the issue by simply
calling SOAP::Utils::encode_data on any of the methods
that are generated through AUTOLOAD.