a dirty old man的用法和样例：
- A dirty old man in the park exposed himself to that beautiful young girl.
- What a terrible joke, you are a dirty old man.
- I have fear that my friend will someday be a dirty old man too.
- The janitor had spread the word about Kessler to the others on the floor, and they shunned him as a dirty old man.
- He is a dirty old man.
- He's a dirty old man.