gistfile1.rb

# coding: utf-8

class Hoge
  def prefix(prefix)
    @prefix ||= []
    @prefix << prefix
  end
  def with_prefix(meth)
    return [@prefix.pop, meth].join('_')
  end
  def foo
    prefix :foo
    self
  end
  def foo_piyo
    '[foo]piyo'
  end
  def method_missing(meth, *args)
    __send__(with_prefix(meth), *args)
  rescue NoMethodError
    super
  end
end

p Hoge.new.foo.piyo