> "I expect this trend will continue, as I strongly doubt that many new green field projects would today choose Perl as the principal development language."
Maybe but checking regularly the CPAN recent updates ( http://search.cpan.org/recent/ ), it seems that Perl is still very active and especially in the activity of providing API or pipe to other technologies/libraries.
At the end, large or medium sized projects are using different programming languages for different tasks and there is no such thing as the "principal development language". Diversity is great...