DSL EXPRESSION:
$new = $["a"]


AST:
* statement block
    * assignment "="
        * direct field value "new"
        * indirect field value "$[]"
            * string literal "a"

a   b   i x                   y                   new
pan pan 1 0.3467901443380824  0.7268028627434533  pan
eks pan 2 0.7586799647899636  0.5221511083334797  eks
wye wye 3 0.20460330576630303 0.33831852551664776 wye
eks wye 4 0.38139939387114097 0.13418874328430463 eks
