to grow a goatee
The term 'dejarse perilla' in Spanish is an expression referring to the act of deliberately allowing one's facial hair to grow specifically in the area around the chin and mouth, resulting in a style known in English as a goatee. This style is often associated with a neat, trimmed beard that does not cover the cheeks, but instead forms a distinct shape around the mouth and chin area. As it's an action, it implies the person's active choice or decision to groom their facial hair in this particular manner.
You're not going to grow a goatee, are you?
The speaker is asking the listener if they plan on growing a goatee. In this context, 'dejarse perilla' is referring to the action of growing a goatee.
My father always grew a goatee since he was young.
The speaker is saying that their father always had a goatee since he was young. Again, 'dejarse perilla' is meaning to grow a goatee.
Juan grew a goatee to appear older.
The text is saying that Juan decided to grow a goatee in order to look older. 'Dejarse perilla' in this context is referring to the action of growing a goatee for cosmetic reasons.