It's, at the very least a doc bug, in that the POD doesn't have this limitation in the CAVEATS. I originally thought it was an implementation bug, but the author responded and said it wasn't.
So sorry, but DBM::Deep doesn't handle objects (i.e. blessed hashes). It only supports anonymous hashes and arrays. Anything blessed will not be stored blessed. I considered adding this feature, but many
classes don't appreciate having their hashes tied. Its on my to-do list for a future release, however.
I think it can be done, but that requires maintaining a separate metadata structure which may require a complete redesign of the file layout.
The Perfect is the Enemy of the Good.