Technically this is the transliteration of that ruby code:

    (def severity :mild)
    (def error_message "OH GOD! IT'S A DISASTER! WE'RE ")
    (if (= severity :mild)
      (def error_message (str error_message "MILDLY INCONVENIENCED!"))
      (when (= severity :terrible)
        (def error_message (str error_message "DOOOOOOOMED!"))))

And if we consider that a good transliteration then I'm not sure why this wouldn't suffice for the second one:

    (def failed_protagonist_names [
       "Larry Potter"
       "Doreen the Explorer"
       "The Incredible Bulk"
    ])

    (def failed_protagonist_names
        (assoc failed_protagonist_names 0 "Gary Potter"))

     ;; => ["Gary Potter" "Doreen the Explorer" "The Incredible Bulk"]