When producing a dump of a Perl hashref containing blessed references, in particular ones produced by the JSON family of modules, the YAML output is broken.


Actual output:

Source: {"a": true, "b": true, "c": 12143}

Decoded JSON: $VAR1 = {
          'b' => bless( do{\(my $o = 1)}, 'JSON::PP::Boolean' ),
          'a' => $VAR1->{'b'},
          'c' => 12143
        };

Dumped as YAML:
---
a: &1 !!perl/scalar:JSON::PP::Boolean 1
b: *1
!!perl/scalar:JSON::PP::Boolean c: 12143

Loaded from this YAML: $VAR1 = {
          'a' => \'1',
          'b' => $VAR1->{'a'},
          'SCALAR(0xaaaac865b678)' => '12143'
        };

I would expect YAML to look like:

---
a: &1 !!perl/scalar:JSON::PP::Boolean 1
b: *1
c: 12143


As you can see, these versions of YAML::Syck fail at round-trip consistency.

Reproducible: Always

Steps to Reproduce:
Install perl, perl-YAML-Syck, perl-Data-Dumper, perl-JSON-XS.

Run this and observe:

perl -MJSON::XS -MYAML::Syck -MData::Dumper -E 'my $s = '"'"'{"a": true, "b": true, "c": 12143}'"'"'; say "Source: $s"; my $x = decode_json($s); say "\nDecoded JSON: ", Dumper($x); my $y = Dump($x); say "Dumped as YAML:\n$y"; my $z = Load($y); say "Loaded from this YAML: ", Dumper($z);'

Actual Results:
---
a: &1 !!perl/scalar:JSON::PP::Boolean 1
b: *1
!!perl/scalar:JSON::PP::Boolean c: 12143

Loaded from this YAML: $VAR1 = {
          'a' => \'1',
          'b' => $VAR1->{'a'},
          'SCALAR(0xaaaac865b678)' => '12143'
        };


Expected Results:
---
a: &1 !!perl/scalar:JSON::PP::Boolean 1
b: *1
c: 12143

Additional Information:
The reason for this bug is merging of this pull request: https://github.com/cpan-authors/YAML-Syck/pull/131

One should note that YAML::Syck has seen lots of activity in the last months, but practically all of that activity was LLM-generated, and that includes tests.

This also affects EPEL 9.