ruby DATA and __END__ heredoc method

heredoc_erb1.rb

#!/usr/bin/ruby

DATA.each_line do |line|
  puts line
end

__END__
Doom
Quake
Diablo

heredoc_erb2.rb

#!/usr/bin/ruby

require 'erb'

time = Time.now
renderer = ERB.new(DATA.read)
puts renderer.result()

__END__
The current time is <%= time %>.

heredoc_erb3.rb

#!/usr/bin/ruby
DATA.rewind
puts DATA.read # prints the entire source file

__END__
meh