Which Attendance has an Opponent of perth glory, and a Round of 9?
CREATE TABLE "attendance_at_home_games" (
  "round" text,
  "date" text,
  "opponent" text,
  "score_aufc_away" text,
  "attendance" real,
  "weekday" text
);
SELECT MIN("attendance") FROM "attendance_at_home_games" WHERE "opponent"='perth glory' AND "round"='9';