No doubt some monks will be wondering about this "little known operator". My apologies to Abigail if he thinks I'm spoiling the fun.

So let's break it down.

First, we have a plain ol' here-doc, written as

<<q
  This is a multiline comment.
q
[download]

Well and good. But, as Abigail points out, this can trigger a warning. The solution is to do something with the resulting string. In this case, we feed it to a regex binding operator: =~ q>>;

This uses the single-q quoting operator to make an empty string. This results in a pretty useless regex, but at least we achieve our goal of doing something with the string created by the here-doc.

So we have something which is equivalent to the following (approximately):

  "this is a comment"  =~ //;
[download]

In summary, there is no "little known << >> operator".

Abigail++ for the neat trick!