The Instruction operation "length" returns the string length of the inputs. If multiple inputs are provided the sum total length is returned.
The example below shows a string of 22 characters, so the result is 22 as it counts the 19 letters and the 3 spaces.
<instruction operation="length">
<input value="nobby the woolly sheep" />
</instruction>
22
The example below shows two strings with 3 characters each, so the result is 6 as the number of carachters in both strings are added.
<instruction operation="length">
<input value="foo" />
<input value="bar" />
</instruction>
6