First things first, 91 is about the absolute maximum that you can get away with, and even then its certainly not a good idea to let it stay that hot.
Invest in the UTH (Under Tank Heater) and a thermostat. The UTH should cover 1/4th to 1/3rd of the bottom of the tank. Simply place it on the far right or far left and make that your warm side (please make sure you use a thermostat, UTH's get up to and over 110 degrees). The size of the UTH then will greatly depend on the size of your tank. If you need to take a measurement. How big is this tank by the way?
Once you have done this you can ditch the heat lamp. With a more modest lighting condition such as those created from regular room lights or from a room with windows, you may notice your corn becoming more active. They are most active in the evenings, mornings, and through out the night, so direct light will likely cause him/her to take cover in a hurry.
Do a quick google search for "Corn Snake Care Sheet" and you will have all the basics at your finger tips.
You could always post pics too. Not only are they fun to look at but they can help us help you!