Board Thread:Support Requests - Designing Your Wikia/@comment-4944666-20151230142245/@comment-4731443-20160102012241

I just stumbled upon a parser function that will let you do this: #pos

If it finds no match, it returns an empty string, which is enough to test your yes/no condition:
 * 1) where  = "word,apple,tree" ##


 * 1) Category Word added ##
 * 2) Category Toy not added ##