DSL EXPRESSION:
if (NR == 1) { $z = 100 }


AST:
* statement block
    * if-chain
        * if-item "if"
            * operator "=="
                * context variable "NR"
                * int literal "1"
            * statement block
                * assignment "="
                    * direct field value "z"
                    * int literal "100"

