I don't think it is possible. One module will be compiled before another and perl will throw a compile time error saying that subroutine such and such is not defined. I've burned with this one before, so don't do it.

Make display subroutines generic enough so they can display anything, regardless of where they come from. And make manipulation subroutines do not care how it will be displayed. Then make another module that uses subroutines from both modules.