www::mechanize check if webpage has updated

Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

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Re: www::mechanize check if webpage has updated by JavaFan (Canon) on Sep 16, 2010 at 12:00 UTC
Store the time you made the latest retrieval. Issue a HEAD request with the 'If-Modified-Since' header set. Don't not do a retrieval if the response is a '304 Not Modified'. Of course, a webserver may not honor the 'If-Modified-Since' header, or send a 200 anyway. There's no guaranteed way of finding out whether a page has changed without retrieving it.	[reply]
Re^2: www::mechanize check if webpage has updated by Anonymous Monk on Sep 16, 2010 at 12:17 UTC
the problem is that the page I want to verify is obtained through a submit_form. So even if I can verify after the http::response object is obtained its fine. Like maybe compare with a saved version	[reply]
Re^3: www::mechanize check if webpage has updated by perlpie (Beadle) on Sep 16, 2010 at 13:15 UTC
Instead of a saved version, just store the hash of the saved version and do nothing if the hash is the same. Instead of hashing the whole page, just hash the portion(s) of the content that you care about. That way different advertisements or updates to the nav links in the header/footer won't throw you off (unless you care about those sorts of changes too).	[reply]
Re: www::mechanize check if webpage has updated by marto (Cardinal) on Sep 16, 2010 at 11:58 UTC
Do you mean page content or what gets displayed to the user? The reason I ask is that pages (or sections of pages, for example a news section) could be updated via AJAX, so while the JavaScript and HTML may not have changed what gets displayed to the user by dynamic methods may be different.	[reply]
Re^2: www::mechanize check if webpage has updated by JavaFan (Canon) on Sep 16, 2010 at 12:11 UTC
Even without dynamic content, what's displayed to the user may change. A page may contain a picture, and the picture (but not the URL) may change (think page counters).	[reply]
Re^2: www::mechanize check if webpage has updated by Anonymous Monk on Sep 16, 2010 at 12:16 UTC
html..more tags get added	[reply]
Re^3: www::mechanize check if webpage has updated by marto (Cardinal) on Sep 16, 2010 at 12:37 UTC
If you purely care about HTML tags use WWW::Mechanize's `content` method to get the page. Then you may want to use one of the HTML parsing modules to compare tags, or if what you're really trying to do is monitor for changes to static HTML content, sore and compare `$mech->content()` periodically for changes.</c>	[reply] [d/l] [select]
Re^4: www::mechanize check if webpage has updated by Anonymous Monk on Sep 16, 2010 at 12:57 UTC
Re^5: www::mechanize check if webpage has updated by marto (Cardinal) on Sep 16, 2010 at 15:26 UTC