Nodes and Strings

Hi all.

Please forgive me if my doubt is already in archive or if it is very
simple but I didn't find it.

I have two sets that I need to compare but the values aren't the same.
Example:

<setA>
    <element>value1</element>
    <element>value2</element>
    <element>value3</element>
    <element>value4</element>
    <element>value5</element>
</setA>

<setB>
    <element>aStringBeforeValue.value1</element>
    <element>aStringBeforeValue.value2</element>
    <element>aStringBeforeValue.value3</element>
</setB>

expected result (for intersection between the sets):

<setC>
    <element>value1</element>
    <element>value2</element>
    <element>value3</element>
</setC>

I want to get the intersection (difference, whatever) between two sets
that haven't the same string values for their elements... (I didn't
found a function like substring, for example, that receives as
parameter
a node list... only for strings... So, I'm resolving this problem with
a
little bit long and confused code.)
Is it possible?

Thanks