You neglected to mention how many teams are in the league. This affects the value of a 5th round pick. Also is the draft order already determined - i.e. do you know your where your pick is going to be?
That being said I think Perry is definitely worth keeping. Guys like Semin, Marleau, Cheechoo, Kostitsyn, and Gagne you can probably pick up later in the draft if you want to. I'd stay away from Gagne and Marleau though I don't think they will be very good next year, but the other guys you might want to draft again, depending on who else is available.
As I said before, it is a 10 team league. I finished 5th, so I will have the 6th pick. Perry's initial value is higher than the rest, so he is liable to be taken if I do not keep him. Kostitsyn will most likely fall due to his name being so new and unknown.