module Roda::RodaPlugins::ContentFor::InstanceMethods

def content_for(key, value=nil, &block)

is no content stored with that key.
stored content with the given key, or return nil if there
under the given key. If called without a block, retrieve
If called with a block, store content enclosed by block 
def content_for(key, value=nil, &block)
  append = opts[:append_content_for]
  if block || value
    if block
      outvar = render_opts[:template_opts][:outvar]
      buf_was = instance_variable_get(outvar)
      # Use temporary output buffer for ERB-based rendering systems
      instance_variable_set(outvar, String.new)
      value = Tilt[render_opts[:engine]].new(&block).render
      instance_variable_set(outvar, buf_was)
    end
    @_content_for ||= {}
    if append
      (@_content_for[key] ||= []) << value
    else
      @_content_for[key] = value
    end
  elsif @_content_for && (value = @_content_for[key])
    if append
      value = value.join
    end
    value
  end
end