use JSON;

my $new_values => [
    machine1 => 100,
    machine2 => 200,
    machine3 => 300,
    machine4 => 400,
];

my $set_virtual_machines = POST(
    'https://api.vps.net/virtual_machines.api10json',
    Accept => 'application/json',
    Content_Type => 'application/json',
    Content => [
        'magic_json_parameter_name' => encode_json($new_values ),
    ],
);