code: function(expr) {
      let result, offset;
      const node = this.node("offsetlookup");
      if (this.token === "[") {
        offset = this.next().read_expr();
        if (this.expect("]")) this.next();
        result = node(expr, offset);
      } else if (this.token === this.tok.T_DOLLAR_OPEN_CURLY_BRACES) {
        offset = this.read_encapsed_string_item(false);
        result = node(expr, offset);
      }
      return result;
    }
docs: Handles the dereferencing