Simply the best date and time manipulation module in my opinion.
The interface is really clean and consistent which is a refreshing change compared to some of the alternatives.
DateTime cover almost all needs for date manip and does so with a modular approach which is more to my liking than the monolithic approach taken by most of the alternatives. Timezones work perfectly and without too much hassle (I had some nasty surprises in other modules about this), date calcul is easy, there are a lot of parsing and formatting DateTime::Format::* modules (which arguably depends on too much other modules but at least you have plenty of choices).
It's not perfect yet but it's constantly improving and has already reached it's goal of being the prime time module in Perl.
I gave this module a good rating since I think you can use it efficiently to dig some information from a xml document in a few lines, however I believe this module is ill-named : compare to a LWP::Simple for example, XML::Simple is much harder to use for a beginner, I would even say it's harder than most of the others XML processing module :
Since the module isn't strict in its structure building, it's easy to get subtle bugs which don't appear with all documents but only on specific instance (e.g. an element that appears most frequently in a list will normally be put in an array, but if it appears alone once, it will not be put in an array, you need to specifically say to XML::Simple you always want this element in an array... to a beginner who check on 2 or 3 examples this can easily bite him !).
This module allows for the most compact xml parsing and accessing among the XML modules (in some case) but not for the most simple, thus it should probably be renamed to something more appropriate (XML::CompactAddressing ? XML::Concise ?) and be advertised for its conciseness, not for its simplicity.