"does not" is one of most vague problem descriptions; right up there with "doesn't work".

A Perl module that produces JSON has two valid choices of what to output: 1) A UTF-8 string that has been tagged as being UTF-8 (from Perl's perspective). 2) A UTF-8 string encoded as a sequence of bytes from Perl's perspective [same as (1) just without the "is utf-8" flag set].

Your code presumes only one of those possibilities. I know that JSON::XS defaults to returning (1) but can be asked to return (2). I haven't looked into what JSON::PP gives.

When dealing with UTF-8 problems in Perl, it is best to use Devel::Peek.

Ok, ok. Although from my perspective, there's little sense in getting (2), it might make sense in situations beyond me.

Apart from that, my use case (where the problem occurred) requires "round trip integrity", meaning: Given a string, I can...
1. -> encode it as JSON
2. -> write it to db
3. -> read it back
4. -> decode from JSON
... and have the same Perl structure as before, or differently said, a structure behaving like before (this tiny differentiation to leave room for: ok, I didn't check if the utf-8 flag was set...)
With my "round trip", relying on JSON::to_json(), the data structure blew from_json() on the "decode from JSON" step.

(Original test script updated). Devel Peek output:

Read more... (1147 Bytes)

You should also Dump the JSON string before you pass it to utf8:: functions.

- tye