Paul Graham is fond of using architectural metaphors in describing programming languages. His favorite is about the arch and the lintel:
Lisp is like an arch. Which of the wedge-shaped stones (voussoirs) is the one that holds up the arch? The question itself is mistaken; they all do. Like an arch, Lisp is a set of interlocking features.(Lintels, on the other hand, are straight stones at the top of an opening, like the header in a doorway. A brute force solution that doesn't scale as well as an arch does.)-- Paul Graham, On Lisp, Chapter 1
Lisp isn't the only programming concept that has this property. In many ways, this also describes Extreme Programming (at least XP done properly, where pair programming, test-first programming, constant integration and the planning game all work together to form a whole that is greater than it's parts).
So now the question is, which stones are missing in Perl's arch. And are we putting the right stones in the right places in Perl6...
