Here are the links in my prior message without adjacent punctuation:

http://www.rubygarden.org/ruby?SingletonPattern

http://www.ruby-talk.org/cgi-bin/scat.rb/ruby/ruby-talk/40537

http://www.ruby-talk.org/cgi-bin/scat.rb/ruby/ruby-talk/40545

http://www.ruby-talk.org/cgi-bin/scat.rb/ruby/ruby-talk/40548

http://wiki.cs.uiuc.edu/VisualWorks/How+do+metaclasses+work%3F