view release on metacpan or  search on metacpan

t/fixtures/example-null.def  view on Meta::CPAN

title 'Example with null';

resource value => {
    type => 'object',
    description => 'the result',
    properties => {
        value  => {
            type => 'null',
            description => 'The Value',
            example => undef,
        },
    },
    required => ['value'],
};