AFAIS it is no macro/function/... where I can return a value, or?
Background is, that I would like to refactor a `GROUP_SORT_EXPR`, that
has grown over time into a forest of IfThenElse()'s.
Depending on what you need your GROUP_SORT_EXPR to do, a classad UserMap (https://htcondor.readthedocs.io/en/latest/misc-concepts/classad-mechanism.html) may be a cleaner way to express the logic.
-greg