Value substitutions
The real-time substitution
mechanism begins from the left of the string and finds the first substitution
instructions. It evaluates that substitution and comes up with a new
version of the string and starts again to evaluate from the left.
Nesting of substitution strings may become complex and care should
be taken to confirm desired results through testing. An example of
using substitution values would be configuring the severity of an
ECI to be $V2$, that is, the severity is set to the value of the second
keyword/value pair. The severity of an ECI may also use something
like $extract(extract(V2,"[",3),"= ",1)$, but this requires a full
understanding of the input string and substitution use. A description
of the scripting system used within the substitution feature and a
complete list of substitution values are listed in Appendix
A, “Substitution Scripting and Values.”