gistfile1.txt

require 'hashie_walker' # https://github.com/monterail/hashie_walker
require 'active_support/inflector'

hash = { 
  "CamelCased" => { 
    "AnotherOne" => { 
      "Foo" => "Bar", 
      "FooFooFoo" => "Dupa" 
    }
  }
}

HashieWalker.walk(hash) do |map| 
  map.key { |key| key.underscore }
end

#=> {"camel_cased"=>{"another_one"=>{"foo"=>"Bar", "foo_foo_foo"=>"Dupa"}}}