msgpack/msgpack-perl — pull request #3 by rurban (2012-06-27 17:30:25+00:00)
Title: support tied hashes (with test case)

The problem is that the length of tied hashes are 0.
The trick was taken from http://cpansearch.perl.org/src/MLEHMANN/JSON-XS-2.32/XS.xs

Note, that I haven't added support for tied arrays