I have amended my script to add in some parentheses which I removed
after Madruger's analysis but, as was shown, at least one of
(ab)cd, a(bc)d or ab(cd) is required [ie (1+1)*9+6].
(added 4 strokes, but removed 4 quoted spaces to leave score unchanged!)

Is the second possable kixtart bug to do with using QUIT within a udf?
I used RETURN as QUIT quit the entire script, not just the udf.