def convert_to_list item
  if item.kind_of? Array then
    "<ul>#{item.map {|part| convert_to_list part }.join }</ul>"
  elsif item.kind_of? Hash then
    "<dl>#{item.map {|k, v| "<dt>#{k}</dt><dd>#{convert_to_list(v)}</dd>"}.join}</dl>"
  else
    "<li>#{item}</li>"
  end
end

def convert_to_list_2 item
  if item.kind_of? Array then
    "<ul>#{item.map {|part| convert_to_list_2 part }}</ul>"
  elsif item.kind_of? Hash then
    "<dl>#{item.map {|k, v| "<dt>#{k}</dt><dd>#{convert_to_list_2(v)}</dd>"}}</dl>"
  else
    "<li>#{item}</li>"
  end
end

list = [1, 2, [3, 6], 5]
p convert_to_list(list)
list = [1, 2, [3, 6], 5, {:a => :b}]
p convert_to_list(list)
p convert_to_list_2(list)
list = [1, 2, [3, ['a', 'b']], 5, {:a => :b}]
p convert_to_list(list)
list = [1, 2, [3, []], 5, {:a => :b}]
p convert_to_list(list)