For the marinade: Mix together all ingredients and set aside to let flavors meld together.
Procedure for the pernil. Preheat oven to 450 degrees. Wash pork under cold running water and pat dry with paper towels. With a sharp paring knife, pierce the flesh. Season with salt and pepper and rub sofrito all over, covering the entire piece of meat. Let marinate for no less than 2 hours but better if overnight. Place pork on an oven rack and place in roasting pan and add enough water to just cover bottom of pan. Put roasting rack in center of the oven and let cook for 20 minutes. Turn the oven down to 350 degrees and let cook until juices run clear. The pork should be firm to the touch. Take the pork out of the oven and let rest for about 10 to 15 minutes. Peel away the skin when cool enough to touch and save, for this is a traditional Caribbean delicacy. Slice meat into bite-size pieces and serve with arroz con gandules.