[DOCS] nothing ever works

The following documentation comment has been logged on the website:

Page: https://www.postgresql.org/docs/9.6/static/plpgsql-statements.html
Description:

Your documentation although it seems straight forward actually never
works.

The dynamic sql section gives example code, it does not execute.

It does not exec in a script block or as plain sql.

Please explain limitations or where the script can actually be executed. 

As a beginner starting out in postgre you can never rely on the
documentation because the same thing happens, you copy the code and make
your modifications and you get syntax error.

The same problem exists with the Perform statement. It does not work as
advertised, you cannot execute it in a function or in a script block.

Clearly define the limitations of your language so that developers don't
waste their time.

Coming from ms sql quite frankly I would never recommend postgress. The
barrior to entry into actualy writing code is too great.