About Symbols | Koans 

* Symbols as strings are not RubyContants 
  i.e :"yo yo" does not include?(RubyConstant)

* Symbols can be built using interpolation

* A Ruby constant is like a variable, except that 
  its value is supposed to remain constant for the
  duration of the program.

* In object-oriented and functional programming, 
  an immutable object is an object whose state 
  cannot be modified after it is created.

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