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=0.3467901443380824,j=1
x=0.7586799647899636,j=2
x=0.20460330576630303,j=3
x=0.38139939387114097,j=4
x=0.5732889198020006,j=5
x=0.5271261600918548,j=6
x=0.6117840605678454,j=7
x=0.5985540091064224,j=8
x=0.03144187646093577,j=9
x=0.5026260055412137,j=10
