if-then语句仅作用于匹配字符串首个实例的问题咨询

各位好，我目前碰到个小麻烦，有些相关知识不太清楚，也没法精准地描述问题（先跟大家说声抱歉）。我写的命令在处理$WARN这个变量时，只会返回第一个匹配到的实例，没办法把所有符合条件的条目都找出来。

先给大家展示下$WARN里的内容，我执行echo "$WARN"后得到的输出是：

(W) 2024-08-30T08:08:52 - Restart is required to toggle support
(W) 2024-08-30T09:59:30 - Failed to download RSS feed at 'https://aaa'. Reason: The connection to the remote server timed out
(W) 2024-08-30T10:00:30 - Failed to download RSS feed at 'https://bbb'. Reason: The connection to the remote server timed out
(W) 2024-08-30T10:00:30 - Failed to download RSS feed at 'https://ccc'. Reason: The connection to the remote server timed out
(W) 2024-09-13T08:59:44 - Failed to download RSS feed at 'http://xxx'. Reason: The remote server refused the connection
(W) 2024-09-13T08:59:44 - Failed to download RSS feed at 'http://yyy'. Reason: The remote server refused the connection
(W) 2024-09-13T08:59:44 - Failed to download RSS feed at 'http://zzz'. Reason: The remot...

我本来想把所有和RSS下载失败相关的条目都筛选出来，但现在的命令只抓到第一条匹配的结果就停止了，有没有大佬能指点下问题出在哪，或者该怎么调整命令才能匹配到所有符合条件的内容呢？

备注：内容来源于stack exchange，提问作者John