When a contains function has two modifiers functions on the two arguments to it then it will not call either of those modifier functions

In XQuery you can have something like:

contains(upper-case($arg),upper-case($searchString)) 

however, in a case like that it will not call upper-case at all, if you change one of them to be lower-case instead for example then both will be called. In the example case if it is called like:

XMLPATTERNS -param path="cookbook.xml" -param sub="MUSHROOMSOUP" mushroomSoup_1.XQ

then it will fail.