Ok here is an update.

MyModule has 50-60 use constant's. If I change those to *CONST1 = sub {42};. The massive number of MyModule::BEGINs drops dramatically and thus saves a heck of a lot of time.
But still sometimes changing a use constant to a *C = sub { ... } does not work. Anyone have any ideas on that?

--habit

P.S. I think it may have to do with the way things are exported...