Hi,

"object" there refers to a JSON object that the MailChimp server is expecting to receive as the value of the merge_fields param, not a Perl object.

The module you are using handles converting your arguments to add_member into the right format for the HTTP call, but as Fletch said you are passing in a hash, which expands to a list, so merge_fields is getting as its value just the first key from your hash (and a bunch of other bogus params are being passed and presumably ignored).

When you pass a reference to the hash instead it is a single data structure and the module will properly convert it to a JSON "object" when making the call to MailChimp.

Hope this helps!