DSL EXPRESSION:
$x =~ "^a.*"."d$"i


AST:
"block" [tt:block] [nt:StatementBlock]
    "=~" [tt:op_eqtilde] [nt:BareBoolean]
        "=~" [tt:op_eqtilde] [nt:Operator]
            "$x" [tt:field_name] [nt:DirectFieldValue]
            "." [tt:op_dot] [nt:DotOperator]
                ""^a.*"" [tt:string_literal] [nt:string_literal]
                ""d$"" [tt:string_literal] [nt:RegexCaseInsensitive]
                    ""d$"" [tt:string_literal] [nt:string_literal]

