libwww is included because CPAN uses it. CPAN belongs in core because you use it to install whatever else you need. Thus, anything CPAN uses belongs in core too. This makes sense, if you think about it: whatever else you want (whether it's XML::Simple or Acme::Bleach) you can easily install _if_ your perl came with what is needed to fetch and install it from CPAN.

This assumes that your distro will come with whatever is needed to build XS (a C compiler, make, and so forth), but Perl comes from a Unix background where that is a mostly reasonable assumption.

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Quidquid latine dictum sit altum viditur.