o replace CORE::GLOBAL::caller and pretend I'm not here?
o proxy DynaLoader/XSLoader bits
  o DynaLoader => Cairo, Date::Simple
  o XSLoader   => Cwd
o prove hook
  o best to not define the trace functions at all in the toplevel
  process, so load a different module as a frontend for tree?  epstree?
o perl -e support for subprocesses in tree mode?