>
>
>> with roomNumber := "User %{%{Stripped-User-Name}:-%{User-Name}} logged
>> in at %S"
>>
>
> The main thing is we have a way of doing it, even if it's a little ugly.
Actually, it looks like you can do a wildcard delete if you pass a 0 length value array.
Could you try
update {
<attribute> -= ANY
}
Bare ANY keyword being magic.
-Arran