module to handle JSON like {"a":1, "a":2}

 A hash tied to the JSON::MultiValueOrdered class acts more or less like
 a standard hash, except that when you assign a new value to an existing
 key, the old value is retained underneath. An explicit delete deletes
 all values associated with a key.
 .
 By default, the old values are inaccessible through the hash interface,
 but can be retrieved via the tied object, however, the fetch_* methods
 provide a means to alter the behaviour of the hash.