CREATE TABLE table_59623 ("Tie no" TEXT, "Home team" TEXT, "Score" TEXT, "Away team" TEXT, "Date" TEXT)

Which away team played against Peterborough United, with a tie no of replay?
SELECT "Away team" FROM table_59623 WHERE "Tie no" = 'replay' AND "Home team" = 'peterborough united'
SELECT "Away team" FROM "table_59623" WHERE "Home team" = 'peterborough united' AND "Tie no" = 'replay'