Add the balsamic vinegar to the skillet and cook until nearly evaporated, scraping up any browned bits from the bottom of the skillet. Add the arugula and toss until wilted, about 2 minutes. Add the tomatoes and the prosciutto and garlic. Cook over high heat for 2 minutes, stirring occasionally; season with salt and pepper. Transfer the arugula to a platter, top with the pork and serve.