Already in the previous edition !
page 436, paragraph after reference/quoting.rb
In the previous example the backslash after Double quoted caused the logical line to be continued
with the contents of the next line.
The backslash is not necessary, especially not in a here document.
print <<HERE
Double quoted
here document.
It is #{Time.now}
HERE
% ruby -w reference/quoting2.rb
Double quoted
here document.
It is 2023-02-13 12:07:56 +0100