The only thing I can think of (and it's not pretty) is to do something like

BEGIN{
%SomePackage::copy:: = %SomePackage::;
%SomePackage:: = ();
# actually, you should probably only move the subs
# and leave the variables etc where they are.
}

package SomePackage;

sub AUTOLOAD
{
  # in here check caller() to see if you're crossing 
  # package boundaries and then call the pre-function
  # wrappers and then call the real function, paying
  # attention to wantarry etc then call the post-function
  # then return the data
}
[download]

slow, ugly, complicated but it should do what you want.