Nesting Is Different From Inclusion

Nesting Is Different From Inclusion
An internal module has access to all the names in its “parent” module.
Here’s an example:
irb(main):017:0> module NewModule
                   Slithy = 'slithy'
irb(main):018:1>
                   module NewInnerModule
irb(main):019:1>
                       puts Slithy
irb(main):020:2>
                   end
irb(main):021:2>
irb(main):022:1> end
slithy
=> nil
However, a nested module does not have access to names included in
its parent:

irb(main):023:0> module IncludedModule
                   IncludedConstant = 'hi'
irb(main):024:1>
irb(main):025:1> end
=> "hi"
irb(main):026:0> module NewModule
                   include IncludedModule # include into outer module
irb(main):027:1>
                   module NewInnerModule
irb(main):028:1>
                      puts IncludedConstant   # This won't work.
irb(main):029:2>
                   end
irb(main):030:2>
irb(main):031:1> end
NameError: uninitialized constant NewModule::NewInnerModule::IncludedConstant
        from (irb):15
There’s one exception. Names included in the global namespace are
available everywhere:
irb(main):032:0> include IncludedModule    # include globally
=> Object
irb(main):033:0> module NewModule
                   module NewInnerModule
irb(main):034:1>
                      puts IncludedConstant    # This will now work
irb(main):035:2>
                   end
irb(main):036:2>
irb(main):037:1> end
hi
=> nil