If you are talking about "Perl resources", then XML looks out of place.

Some additions in this category:

• backreferences
• lookahead/lookbehind
• recursive regexp
• pack/unpack
• vec
• splice
• array slices
• hash slices
• nested map
• eval
• the Schwartzian transform
• BEGIN / END
• one-liners

If you talk about programming resources in general, then you should include:

• databases
• DB files
• CGI
• LWP
• signals
• Web services
• mod_perl
• templates
• a Parser