In my MW 2.28.2 site, I placed the following code into a page:
{{#invoke:String|len|This is a Test}}
It did not execute as expected, it only appeared as text.
From the documentation page on the string module [0], it is not clear to me how to enable this capability.
How do I enable the String Module in my site?
[0] https://www.mediawiki.org/wiki/Module:String
-Rich