如何使用PostgreSQL在CASE内循环？

CREATE OR REPLACE FUNCTION loop_with_case()
RETURNS VOID AS $$
DECLARE
    counter INT := 1;
    max_counter INT := 10;
BEGIN
    WHILE counter <= max_counter LOOP
        CASE
            WHEN counter < 5 THEN
                -- 执行某些操作或返回某些结果
                RAISE NOTICE 'Counter is less than 5: %', counter;
            WHEN counter >= 5 AND counter < 8 THEN
                -- 执行其他操作或返回其他结果
                RAISE NOTICE 'Counter is between 5 and 7: %', counter;
            ELSE
                -- 执行其他操作或返回其他结果
                RAISE NOTICE 'Counter is greater than or equal to 8: %', counter;
        END CASE;
        
        counter := counter + 1;
    END LOOP;
END;
$$ LANGUAGE plpgsql;