How many times was pernell whitaker an opponent?
CREATE TABLE "list_of_boxing_quadruple_or_four_divisio" (
  "number" real,
  "name" text,
  "titles" text,
  "date" text,
  "opponent" text,
  "result" text,
  "defenses" real
);
SELECT COUNT("date") FROM "list_of_boxing_quadruple_or_four_divisio" WHERE "opponent"='Pernell Whitaker';