Cacher is the code snippet organizer for pro developers

$ ruby19 test_class_eval.rb 
"a"
50
"b"
42

$ macruby test_class_eval.rb 
"a"
50
"a"
42

class C
  @@class_eval = 'b'
  CONST = 42

  module M
    @@class_eval = 'a'
    CONST = 50
    p M.class_eval { @@class_eval } # => 'a'
    p M.class_eval { CONST }        # => 50
  end

  p M.class_eval { @@class_eval }   # => 'b'
  p M.class_eval { CONST }          # => 42
end

C.new