SSRS 2005 SQL Server Reporting Services 2005 Dataset Filter IN CLAUSE: Syntax? Broken? Bug?

I can't seem to get a dataset filter to work in SSRS 2005 with an IN CLAUSE.  Assume I am trying to select only Region 1, Region 2, Region 3.  Have tried:

Region 1, Region 2, Region 3 (does not work)
Region 1   (works, but it's only 1 value)
Region 1, Region 1 (does not work)
Region 1,Region 1 (does not work)
"Region 1","Region 1" (does not work)
"Region 1",  "Region 1" (does not work)
Region 1 Region 1 (does not work)
Region 1/Region 1 (does not work)
"Region 1, Region 1" (does not work)

I'm coming to the conclusions that In Clause filters do not work!