fixed erroneous usage example
fixed erroneous usage example

git-svn-id: cf87fca8705a0432a1a4a9b03466416ae3b9b79b@13 e01bff1d-8c55-0410-8b62-59462f3e2d4b

sombr/protobuf-perlxs,sombr/protobuf-perlxs,sombr/protobuf-perlxs