TASK DEFINITION: Given a sentence, generate a new sentence by performing small changes on the sentence. Here, make sure that the changes are semantically related and syntactically similar to the input. And the generated sentence should have high commonsense plausibility, that is to have reasonable probability of it being true.
PROBLEM: You are likely to find a football stash in an envelope .

SOLUTION: You are sorry to find a th parcel in an envelope .

PROBLEM: If you want to read a book then you should turn on the light.

SOLUTION: If you want to read a book then you should slow on the light .

PROBLEM: If you accept to have a membership then you should make an expression .

SOLUTION:
If you want to have a haircut then you should make an appointment.