From the Simple Present to the Future Perfect Progressive
I am an ESL teacher, but this is generally not the example I use in class when I am explaining tenses. However, I do try to avoid the classic grammar book examples which always seem to involve telephones ringing, taking showers, walking home, having dinner and someone coming into the room (I was having dinner when the phone rang. Sharon came into the room after I had eaten dinner. The phone had rung three times before Sharon entered the room. I had been thinking about taking a shower for fifteen minutes when Sharon entered the room. Before Sharon entered the room, she walked home. Sharon had heard a phone ring in a neighboring house while she was walking home. I wonder when Sharon will enter the room again, and if the phone will have rung before she next enters the room. How many showers will I have taken by that time? And why is Sharon always entering my room?).
There is some grammar planet where phones are always ringing and showers are always being taken and Sharon always enters (but never exits) a room.