There are at least 8 companies that I'm aware of recruiting for "Perl developers" in London. I think that are all expanding, rather than replacing existing staff, most want "senior" people, and in a couple of cases I believe that they're wanting 12 or so people over the course of the next months. So even if some of these posts are filled, it just starts the merry-go-round by transferring the vacancies elsewhere.
Herein lies a problem.
There aren't that many "senior perl" people looking for new jobs in London. In particular, a lot of these companies seem to want someone with 3-5 years experience in template system of choice, who likes making websites, knows the current web standards, and is keen on the salary ranges offered.
Trouble is that everyone else is looking for exactly the same sort of people. And that they seem surprised that they can't find anyone. Or that people start asking
It's probably a side effect of Perl. It's not taught at universities, so there isn't a ready made supply of cookie cutter graduates to slip into dull jobs. It's not used by major IT contractors (think Capita or EDS), so they aren't busy generating people moving on with 3-5 years' experience of Perl. Perl is something people tend to find by themselves, so is likely to bias itself to the more self-motivated (and potentially therefore, on average, above average) IT person. Also Perl is seen by some as a fun language - this has lead to a class of people who preferred to stick with Perl and let the money go down during the quiet times, rather than change to other skills and follow the money elsewhere. But when "Perl" jobs dried up after the last bubble burst, what do people do? If you want the money, you shift your CV to emphasise the well paid skills, i.e. not Perl.
The upshot is that there aren't enough "Perl" people for these new jobs. There aren't the less experienced developers who would see these "senior" jobs as a move up, because there weren't the more junior jobs for them over the past few years. There are people with more experience than the range the employer suggests, but strangely they've been working elsewhere, so earn more than the employer wants to offer for just the skills they seek. And there are people who used to do Perl, who aren't now, who are likely to be earning more than the employer wants to offer.
So what can the employers do to recruit and retain staff? Logically:
After all, we pride Perl on its shallow learning curve, so its similarity to many other languages (sed, awk, C, C++, Java, PHP) means that smart people don't take long to become effective in it. Sure, you can't fill your entire team this way, but you don't need everyone to be the same cookie-cutter Perl expert.