:: {a:r4, b:r4, r:{b:(b,b)?}}

// *** Operator errors.
+-1
/*

// *** Case errors.
NoT true
not TrUe
true OR falSe

// Scope and name errors.

'+' + '-'
With(r, a%/b)
With(r, a%/@b)
With(r, -a%/b)
With(r, a/b%)
With(r, a/-b%)
With(r, (a/b)%)
