I think training is the way to go. That includes training interns and programmers from different programming languange. It is not easy and not for everyone, but I think training is needed in any company culture that values continuity of its business.

Being able to teach stuff to other people has benefit me a lot. I learned from teaching that people have different way of thinking and different speed in acquiring new knowledge. That has helped me in growing from a junior programmer to the technical lead in 2 years of my first job.

So I guess, when a senior programmer becomes a technical lead, he needs to be able to pass on his knowledge to their underlings, whether they are experienced Perl programmers, experienced Java programmers, interns, or any junior programmers.