For the managed package runtime, if an input to your custom function is of the type List<Object>, the input is saved to a VLOCITY-FORMULA-LIST key. To retrieve the input, use code that retrieves this key.
This information is for Omnistudio for Managed Packages. For Omnistudio on standard runtime, see Omnistudio Help.
For example:
static List<Map<String, Object>> FUNCTION(List<Object> inputs)
{
List<Object> listInput = ((Map<String, Object>)inputs[0]).get('VLOCITY-FORMULA-LIST');
Object variableInput = inputs[1];
// Rest of Function
}
For a full working example, see the toObjArray function in Sample Apex Code for a Custom Function in Omnistudio for Managed Packages (Managed Package).