Is there a way to have CONSTANTS in a "pipeline"(AKA MAPPING)?

What I would like to do is have settable CONSTANTS to do things like set limits within a mapping that would be LIKE parameters, but isolated from the outside world. I would hate to change pipelines made for running these mappings(er pipelines) simply because I needed to add a new test value.

There could be a lot of uses for such constants. OH, and it would ALSO be great if the mappers, or other objects, could use values created from previous lines in that mapper.

Steve