Strings in lua can't be added, you need to use the concatenate operator (+ is a operator, concatenate is putting a string together), that operator has 2 points, so "result .. c" is result and c.
The next version holds some changes to the object model, but the old writing will stay compatible.
For getting values, in the upcoming version you can write
If you want to write something there it's
Now let's get a string, concatenate something and save it back.
local obj = getObject("Values[name]")
local str = obj:getStr(VValueString)
str = str.."_test"
In the upcoming version this will also work:
Values.name.String = Values.name.String.."_test"