The Perks of Being a Wallflower might as well come with a question mark at the end.
Patrick describes Charlie's wallflower nature at the end of Part 1: "You see things. You keep quiet about them. And you understand" (1.10.108). This is a virtue, according to the Scooby gang, because they all raise their drinks, "and the whole group said, 'To Charlie'" (1.10.112).
That's a wonderful little toast, yes, and it's definitely nice that Charlie's being accepted. But they're toasting him for keeping quiet, and his characteristic silence causes a lot of mental turmoil for our favorite wallflower.
Think about it. When he sees a boy force his girlfriend to perform sex acts on him, Charlie keeps quiet. When Patrick starts kissing him even though he isn't gay, Charlie keeps quiet. And even though he is very young when his aunt molests him, Charlie keeps so quiet that he represses it entirely until it bubbles to the surface so fast he ends up hospitalized. We have a hard time including "hospitalization" in our list of perks.
So what are the perks of being a wallflower? Really, we're asking.