CoCoA » CoCoA-5

After "use" the interpreter expectes the special poly ring constructor, such as QQ[x,y], with the unconventional meaning of the square brackets and interpretation of, x and y.
In this context round brackets are only allowed for writing ZZ/(3).
Now, whereas in general it is indeed ambiguous at parsing level, as in

Use NewQuotientRing(R,I)[X];  -- the ring R/I[X]?
Use ListOfRings(A,B)[n];  -- the n-th element in the list?
Use Func(A)[w]; -- ????

a single function call is not, as in

Use NewFractionField(R);

It would be very handy. How difficult is it to implement?