I think part of the problem here is the versions required for the dependencies of
Test-Simple are greater than those which come with the core ActivePerl distribution. ActiveState doesn't supply ppm packages of the core ActivePerl modules, in order to prevent possible breakages of basic functionality. From that point of view, it's understandable why packages which depend on newer versions of core modules aren't supplied.
This problem is being addressed to a certain extent with PPM4 (coming with ActivePerl 819 and higher), where it is possible to install packages to different areas, including that where the core modules reside. However, compatibility must be maintained with previous ActivePerl versions, where it was not so easy to upgrade core modules. For now, probably the best way to approach this from a ppm standpoint is to use the external repositories mentioned in other replies.