What is the average match when the singapore armed forces played away against perak fa (malaysia)?
CREATE TABLE "afc_cup" (
  "match" real,
  "date" text,
  "round" text,
  "home_away" text,
  "opponent_team" text,
  "score" text
);
SELECT AVG("match") FROM "afc_cup" WHERE "home_away"='away' AND "opponent_team"='perak fa (malaysia)';