gistfile1.rb

# http://yehudakatz.com/2010/02/21/ruby-is-not-a-callable-oriented-language/

module DoAsYouPlease
  Object.send :include, self
  def method_missing(name, *args, &block)
    self.class.const_get(name).call(*args, &block)
  end
end

Foo = proc { 42 }
Foo   # => #<Proc:...>
Foo() # => 42

gistfile2.rb

def callable_oriented(&block)
  scope          = block.binding
  eigenclass     = class << scope.eval("self"); self; end
  method_catcher = Module.new do
    define_method(:method_missing) do |name, *args|
      name = name.to_s
      return super(name.to_sym, *args) unless name =~ /^[A-Z]/ or scope.eval("local_variables").any? { |n| n.to_s == name }
      scope.eval(name).call(*args)
    end
  end
  eigenclass.send :include, method_catcher
  yield
end

foo = proc { 42 }

callable_oriented do
  p foo
  p foo()
end

mind = 💥