I know a guy working at JPL doing Perl stuff for internal use still. I give him a hard time about it, but it's a lot cooler than Social_Widget_0003993986 in any other language you care to name.
Are you referring to the work or Perl? Most programmers I know working in a scientific area switched to Python years ago and run away screaming when they hear the work "Perl".
I cut my teeth on perl and don't run screaming when I see to this day. Perl has an undeserved bad rap. I like python as much as the next guy but frankly Perl does some things way better than python. And don't get me started on Pythons rules around scope.
Actually, it's been known for quite awhile that there's a factor of 2 to 3 times in productivity. That's not really marginal. Talent far outstrips that, though.
It doesn't equal utility, but it does equal quality, at least to the extent that bugs per SLOC matter. This has also been known for awhile, with data to back it up.
I'm not sure that's true. Though it obviously depends more on the programmer themself, the semantics of a language can make it easier, at least, to write higher quality code. For example, bounds checking removes a whole class of bugs (probably the most common in C) from the equation. I disagree that this effect could be described as "marginal".