It is reliable for me to use modification time. Does the modification time change when page changes, meaning is it RSS feed requirement?

Yes and no. There are recommendations and requirements (see rfc), but web servers/sites frequently ignore such.

In reply to Re^7: Parsing ITEM Tag from RSS feed using XML::RSS::LibXML by Anonymous Monk
in thread Parsing ITEM Tag from RSS feed using XML::RSS::LibXML by mr_p

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