How to copy an exchange property to the global options?

[Ron Cecchini]

I'm trying to pass back the # of things I've processed in a route back to the 
calling Java.

This log() displays the correct number:

.log(LoggingLevel.INFO, "Processing ${body.size} Things ...")

I then tried putting that ${body.size} in a GlobalOption on the CamelContext so 
I can access it later:

.process(exchange -> exchange.getContext().getGlobalOptions().put("NumThings", 
simple("${body.size}").toString()) )

However, the above, and a few variations of the simple(), causes this:

System.out.println(String.format("*** Processed %s Things", 
camContext.getGlobalOption("NumThings")));

to gives this:

*** Processed Simple: ${body.size} Things

I just can't figure out how to do the evaluations and get that value in the 
GlobalOptions.  (I googled and googled...)

Or maybe there's a better way to store it in the CamelContext?

Thanks.