Is this JSON producer a learning exercise, or is it to create a JSON encoder that does something the others don't? Is the issue that you're not allowed to install 3rd party modules? I'm just curious. There may be a more robust solution that consumes less work than the path you're currently on. Even if your specification is to not use any modules from CPAN, modules such as JSON::Tiny are set up to allow copy/paste embedding if your situation requires it.