{ "single": { "&": "join_core", "list": "^@.one" }, "two": { "&": "join_core", "list": "^@.two" }, "three": { "&": "join_core", "list": "^@.three" }, "custom": { "&": "join_core", "list": "^@.three", "separator": " and ", "lastseparator": " but also " } }

{ "one": ["one"], "two": ["two", "things"], "three": ["first", "second", "third"] }