dplyr 0.7 equivalent for deprecated mutate_

I cannot find in dplyr 0.7 a way to replace the mutate_ function which is going to be deprecated.

The mutate_ function is useful in my use case : I store in a database (string format) many instructions (that can be filtered if needed) and apply these instructions to one or several data frames.

For example :

dplyr::tibble(test = "test@test") %>% 
  dplyr::mutate_(.dots = list("test2" = "substr(test, 1, 5)",
                              "test3" = "substr(test, 5, 5)"))

Is there a way to do this with dplyr 0.7 keeping variables and instructions as character?