Just complementing Florian Pfeffer
There's another option possible that work in same way:
('PLACEHOLDER' = ('$$IP_CUSTOMER_NAME$$', 'Adam'',''Ian'))
and
in("<your attribute to be filtered", '$$IP_CUSTOMER_NAME$$')
The difference is from first '' and last '', so if you don't have multi parameters you can pass like this:
('PLACEHOLDER' = ('$$IP_CUSTOMER_NAME$$', 'Adam'))
Regards, Fernando Da Rós