The new $cleanmulti() function seemingly only works with multi-value tags but not with multi-value variables.

$setmulti(_test,A; ; B)
$cleanmulti(_test)
$join(%_test%,+)

The above file naming script demo outputs "A++B" in Picard 2.8.3 while it should output "A+B". If I remove the underscore prefixes from that example, the function works as intended.

I discovered this because there were lots of unintended side effects (i.e. too many joiner spaces) in my naming script due to the new behaviour that empty values are no longer automatically discarded. (My script makes heavy use of multi-value variables for string concatenation with optional string segments.)