If you are strictly going for perch like you mentioned, then a stiff rod would not serve you any good. A stiff rod will give you the backbone to set the hook on a fish with a bony mouth such as a pike, that is heavy and you can pull it in without breaking your rod. For perch, all you need is an ultralite, that gives you the sensitivity you need to feel every nibble. A perch has a very thin, paper like mouth. An ultralite is more than capable of getting a good hook set.
However, if you want a more all around rod, then a medium light would be better, or a medium if you plan on going for pike or walleye or anything along that line.