They are (now) - which version are you using? They are documented in IC615 documentation:
Squiggle Arrow (~>) Operator
The squiggle arrow (~>) operator is a generalization of the arrow operator. It works the same way as an arrow operator when applied directly to an object, but it can also accept a list of such objects. It walks the list applying the arrow operator whenever it finds an atomic object.
The underlying functions for ~> operator are the setSGq and getSGq functions, which set and retrieve the value of an attribute or a property. For example,
setSGq(obj value prop) ; is equivalent to:
a=getSGq(obj prop) ; is equivalent to:
info=getSGq(cvId objType) ; is equivalent to:
setSGq(rect list(10:10 100:120) bBox) ; is equivalent to:
... <snippety snip>
In fact I filed CCR 819675 for this a while ago.
Is this what you are looking for?