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


AST:
"block" [tt:block] [nt:StatementBlock]
    "=" [tt:equals] [nt:Assignment]
        "$new" [tt:field_name] [nt:DirectFieldValue]
        "$[]" [tt:$[]] [nt:IndirectFieldValue]
            ""a"" [tt:string_literal] [nt:string_literal]

a   b   i x          y          new
pan pan 1 0.34679014 0.72680286 pan
eks pan 2 0.75867996 0.52215111 eks
wye wye 3 0.20460331 0.33831853 wye
eks wye 4 0.38139939 0.13418874 eks
