My fault was that I read it as JSON has a bug in escaping quotes!

( JS - contrary to Perl - doesn't give single and double quotes different meanings, but that doesn't mean they need to be escaped, so no bug! )

so whats happening here is that Jeppe wants the data altered, and IMHO this should already be done on Perl's side before escaping.

Your suggestion of a general s/'/\\'/g would only work if the JSON output doesn't use single quotes as delimiter.¹

update

¹) ah sorry, I didn't know that single quotations are invalid in JSON

from JSON::PP

   allow_singlequote
           $json = $json->allow_singlequote([$enable])

       If $enable is true (or missing), then "decode" will accept JSON
+ strings
       quoted by single quotations that are invalid JSON format.
[download]