Existence of String in a List of Strings using XPATH Expressions

Question

Hi I want to build a Expression using Xpath to check whether a String let say "XY" exist in a list of string say ["XY","PP","DD"...]

also the expression should return boolean (True/False)

Thanks in Advance

I tried contains function but contains only work with 2 string and here in my case I have a list of string to compare