gistfile1.rb

# http://news.ycombinator.com/item?id=1571894
# A quick tips when creating block DSLs in Ruby:

def search(&blk)
  if blk.arity == 1
    blk.call(self)
  else
    self.instance_eval(&blk)
  end
end

# Then the user can decide what he want to use:
Foo.search { bar }
Foo.search { |s| s.bar }