gistfile1.rb

# call methods like constants

module Foo
  def self.bar
    'tadam'
  end
end

Foo::bar # => tadam

# methods can be capitalized

module Foo
  def self.Bar(default='boo')
    default
  end
end

Foo.Bar # => "boo"
Foo::Bar() # => "boo" - parenthesis are necessary to distinguish from constant
Foo::Bar 'yo' # => "yo"

# previously it was very popular to have a method with the same name as a class to create a new instance of the class
Nokogiri # => Nokogiri 
Nokogiri 'xml' # => #<Nokogiri::XML::Document:0x3feb951e84c4 name="document">