use 5.012; # strict, //
use warnings;
use JSON 4.0;
use Data::Dumper;

print "JSON::VERSION = $JSON::VERSION\n";

my $json = JSON->new;
$json->boolean_values(0,1);


test@BruceDEV:~$ perl Perl-Testing/JSON-boolean_values.pl
JSON::VERSION = 4.02

Can't locate object method "boolean_values" via package "JSON" at Perl-Testing/JSON-boolean_values.pl line 11.

##</code><code>##

Debian GNU/Linux 10

ii  libjson-perl                          4.02000-1                                   all          module for manipulating JSON-formatted data
ii  libjson-xs-perl                       3.040-1+b1                                  amd64        module for manipulating JSON-formatted data (C/XS-accelerated)

##</code><code>##

package JSON;


use strict;
use Carp ();
use Exporter;
BEGIN { @JSON::ISA = 'Exporter' }

@JSON::EXPORT = qw(from_json to_json jsonToObj objToJson encode_json decode_json);

BEGIN {
    $JSON::VERSION = '4.02';
    $JSON::DEBUG   = 0 unless (defined $JSON::DEBUG);
    $JSON::DEBUG   = $ENV{ PERL_JSON_DEBUG } if exists $ENV{ PERL_JSON_DEBUG };
}


[...]

=head2 boolean_values (since version 4.0)

    $json->boolean_values([$false, $true])

    ($false,  $true) = $json->get_boolean_values

By default, JSON booleans will be decoded as overloaded
C<$JSON::false> and C<$JSON::true> objects.