Then maybe a first step would be to create the strings:

"name:Joe"
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This is somewhat weird, because JSON usually doesn't encode information in tagged strings but as "objects" (anonymous hashes in Perl).

Maybe you can show us an example of your data structure where you have two persons, Joe and Jane?

Usually, with JSON, you don't build the string but build the appropriate Perl data structure and export that data strucutre as JSON using one of the modules. But until you show us what the data structure should look like, we can't really help you building it.