for a given class, find all subclasses

i found the solution (by pit capitain) at
http://groups.google.com/group/comp.lang.ruby/browse_thread/thread/e812c7cef446a96
, it works, but i don't understand it.
--------------------------------------------------------
   require "enumerator"

   def get_subclasses(klass)
     ObjectSpace.enum_for(:each_object, class << klass; self;
end).to_a
   end

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i don't understand what "class << klass; self; end" does. can someone
rewrite and make it longer?


Dorren