How about using <> to represent Here Document?
"<<" is a frequently used method in text manipulation. Meanwhile, it's also the beginning token of a here-document.
Sometimes it may be confusing to newbies.
Unlike Perl, in which "<>" is a very very frequently used operator to read lines from a filehandle, in Ruby, "<>" has no meaning. So I think it can be used to represent Here Document, so as to reduce the possibility of misunderstanding method "<<" and here-document token "<<". And In my opinion, <> is more clear than <<, because it looks like kind of brackets.
str = <SECT1>.upcase + <SECT2>.downcase aaaaaa SECT1 XXXXXX SECT2
may be clearer than:
str = <<SECT1.upcase + <<SECT2.downcase