如果有人在RubyonRails中寻找在html模板中注释多行的方法，那么=begin=end可能会有问题，例如：

<%
=begin
%>
  ... multiple HTML lines to comment out
  <%= image_tag("image.jpg") %>
<%
=end
%>

将失败，因为%>正在关闭image_tag。

在这种情况下，这是否是注释掉可能是有争议的，但我更喜欢用“if false”块括住不需要的部分：

<% if false %>
  ... multiple HTML lines to comment out
  <%= image_tag("image.jpg") %>
<% end %>

这会奏效的。

使用以下任一项：

=begin
This
is
a
comment
block
=end

or

# This
# is
# a
# comment
# block

是rdoc目前唯一支持的两个，我认为这是一个很好的理由只使用这些。

=begin
My 
multiline
comment
here
=end

下面是一个示例：

=begin 
print "Give me a number:"
number = gets.chomp.to_f

total = number * 10
puts  "The total value is : #{total}"

=end

放置在=begin和=end之间的所有内容都将被视为注释，而不管其间包含多少行代码。

注意：确保=和begin之间没有空格：

正确：=开始错误：=开始

  def idle
    <<~aid
    This is some description of what idle does.

    It does nothing actually, it's just here to show an example of multiline
    documentation. Thus said, this is something that is more common in the
    python community. That's an important point as it's good to also fit the
    expectation of your community of work. Now, if you agree with your team to
    go with a solution like this one for documenting your own base code, that's
    fine: just discuss about it with them first.

    Depending on your editor configuration, it won't be colored like a comment,
    like those starting with a "#". But as any keyword can be used for wrapping
    an heredoc, it is easy to spot anyway. One could even come with separated
    words for different puposes, so selective extraction for different types of
    documentation generation would be more practical. Depending on your editor,
    you possibly could configure it to use the same syntax highlight used for
    monoline comment when the keyword is one like aid or whatever you like.

    Also note that the squiggly-heredoc, using "~", allow to position
    the closing term with a level of indentation. That avoids to break the visual reading flow, unlike this far too long line.
    aid
  end

请注意，在本文发表的时候，stackoverflow引擎没有正确呈现语法着色。测试它如何在您选择的编辑器中呈现是一项练习

#!/usr/bin/env ruby

=begin
Between =begin and =end, any number
of lines may be written. All of these
lines are ignored by the Ruby interpreter.
=end

puts "Hello world!"