JSON::PP and Cpanel::JSON::XS don't have this problem somehow.
From my reading of the documentation of the former (especially the MAPPING section), it has the same problem for the same reasons.
the whole thing is a tangled mess of wrongness
Perl has monomorphic operators and polymorphic values. Every time someone tries to flip that, whether encoding arbitrary data structures to monomorphic values via a polymorphic visitor pattern, the smart-match experiment, or (as I already mentioned in this story's comments) polymorphic operators for data structure dereferencing, these problems occur.
Regardless of whether anyone believes that Perl's operator/value design is good or useful, that's how the language works. Working at cross purposes is an exercise in frustration. (I'll leave analogies about duck typing, contravariance, casting, and type erasure to people who like debating programming language design.)
From my reading of the documentation of the former (especially the MAPPING section), it has the same problem for the same reasons.
the whole thing is a tangled mess of wrongness
Perl has monomorphic operators and polymorphic values. Every time someone tries to flip that, whether encoding arbitrary data structures to monomorphic values via a polymorphic visitor pattern, the smart-match experiment, or (as I already mentioned in this story's comments) polymorphic operators for data structure dereferencing, these problems occur.
Regardless of whether anyone believes that Perl's operator/value design is good or useful, that's how the language works. Working at cross purposes is an exercise in frustration. (I'll leave analogies about duck typing, contravariance, casting, and type erasure to people who like debating programming language design.)