Make sure to compare against the logic for CBOR hooks which is sufficiently generic to serve multiple serializers. Right now, the only incompatibility is that for Sereal, FREEZE needs to return a single data structure instead of a list. That is quite a bit more efficient for simple data structures and also easier on the implementation, particularly for more static languages than Perl. Comments welcome. This is a proposal.
In other words, non-incremental Snappy compression is no longer valid Sereal in protocol version 2.