If at any time you use SSSTAGE1 as a string in your program, it may change how it gets converted to JSON by the JSON.pm module. JSON.pm will internally try to use JSON::XS if possible, which has a heuristic for encoding values like this that can be problematic.

If you switched to the JSON::MaybeXS module instead, it would likely work as you expected. Internally, it will try to use the Cpanel::JSON::XS module, which has better behavior for values like this than JSON::XS.