DSL EXPRESSION:
for(k,v in $*) {if (k != "x") {unset $[k]}}; $j = NR


AST:
* statement block
    * double-variable for-loop "for"
        * local variable "k"
        * local variable "v"
        * full record "$*"
        * statement block
            * if-chain
                * if-item "if"
                    * operator "!="
                        * local variable "k"
                        * string literal "x"
                    * statement block
                        * unset "unset"
                            * indirect field value "$[]"
                                * local variable "k"
    * assignment "="
        * direct field value "j"
        * context variable "NR"

x=0.34679014,j=1
x=0.75867996,j=2
x=0.20460331,j=3
x=0.38139939,j=4
x=0.57328892,j=5
x=0.52712616,j=6
x=0.61178406,j=7
x=0.59855401,j=8
x=0.03144188,j=9
x=0.50262601,j=10
