Including standardized information in scriptable email templates

Has anyone been able to  include a scriptable email sub template?  the documentation says you can include another scriptable template inside your current email like this:
  [INDENT] [/INDENT]
  [LEFT]For example, to insert a template in the NetSuite file cabinet with the internal ID of 123, you could use:[/LEFT] 
<#include "id:123">   [LEFT]To insert a template by referencing the URL, you could use:[/LEFT] 
<#include "http://company.com/templates/myheader.ftl">   [INDENT] [/INDENT]
But when I try to replicate this using either method, I get nonsensical parse errors like this:

[ATTACH=CONFIG]n344755[/ATTACH]

It says it found a backslash, but of course there is no backslash in the  include statement, only forward slashes.