I have not used Modperl::Registry or SOAP::Transport, so the purpose of the "Hello.pm" handler is not clear to me BUT I have written perl modules for use under mod perl and if this handler module is used the same way by Modperl::Registry:

package Hello;
  
sub hello {
   return "hello, world";
}

1;
[download]

Then the function "hello" should be called "handler" -- that is the function mod_perl uses at instantiation of the package, much like a function "new" is required to instantiate an object. Are you sure this is not the case here? Just a thought.