Document the standard OUTPUT format for newcomers

Closes #4616

Author: coke

doc/Language/intro.rakudoc

@@ -63,5 +63,19 @@ on the raku.org site. These include articles, books, slide
 presentations, and videos.
 =end item
 
+=begin item
+You will see examples throughout the document, like so:
+
+=for code
+my @a = 1, 2, 3;
+@a»++;
+say @a;             # OUTPUT: «[2 3 4]␤»
+
+Note on the last line, there is a comment, starting with C<# OUTPUT:>, that shows what the example outputs.
+The output is wrapped in C<«»> quotes (also a valid quoting construct in Raku!), and may include a C<␤>, which
+is the Unicode character "Symbol for Newline" - to indicates where in the actual output a literal newline would
+appear.
+
+=end item
 
 =end pod