Checking if 1 or items in 1 delimitedString exist in another

Hi all,
Which is the best way to check if an item or more of one delimited string exist in another?
I'd like to pass 2 delimited strings to a UDF and get back TRUE if at least one item of
the first delimited string exists in the second delimited string.

delStr1="US,FR,DE,PL"
delStr2="GB,DE,CA"
delStr3="CN,DK,IT"

udf_CheckDelimitedString(delStr1,DelStr2)= TRUE (DE)
udf_CheckDelimitedString(delStr2,DelStr3)= FALSE

Thanks in advance for your help.
W.

Why don't you use CHARINDEX function instead.