Well, that was fast.
As "Anonymous" (ahem) correctly noted,
"that is the flashing for the orange vent pipe that goes out the roof."
Here's a picture:
Unfortunately, however, according to the official bylaws of this blog, we cannot award the promised three points to anonymous commenters. Should "Anonymous" choose to identify him- or herself, we would be more than happy to designate him or her as our champion. But in the meantime, our hands are tied.
In other words, "Anonymous," the ball is in your court......