Options undocumented
It seems there are options for both serialize() and unserialize(), but I do not know what they do. I have read the following comment but I don't know what it means.
Indicates whether multiple values in data are concatenated to multiple MessagePack arrays.
Perhaps an example would help?
Not sure why that exists, maybe somebody else wrote it. As I understand the code:
If you serialise an array, you get a MessagePack stream that represents an array that contains the values that the original array contains. You get what you give.
With the "multiple" option, when you serialise an array, you instead get multiple concatenated independent MessagePack streams each representing an item of the original array. The MessagePack data will not contain the original array anymore.
Probably a convenience thing for some use case. You could also do this manually, serialising each array item and then concatenating all the results.