First of all, we should organize our replies a bit more and include in the topic maybe the sections we took a look at - that makes it easier to find unclean sections for those who want to join work - it seems like organization and afterwards cleaning up must take place at every level :) but at least at this level, we know that this quest will end and all our comments will go into the big bit bucket some time afterwards ...

I took a look at the Nested Data Structures section

This section does not really need reworking, as there are only few questions and few answers, and all answers are good and matching to the questions. One could add references to the Perl man pages to "How do I make an array of arrays ?" and/or combine the answers into one writeup, but IMO, there's nothing to be taken away in this section.