|Don't ask to ask, just ask|
Thank you all for your valuable insights.
I was not really planning to do such a test, I was mostly surprised by the fact that such a test at all was available for Perl. Knowing the Perl-community mainly through PerlMonks and YAPC, I did not expect such tests to be taken very serious by those who really know Perl.
But then again, it is probably very easy to put up a dynamic web-site with some multiple choice tests and thus relieve unsuspecting passers-by from 25 USD for a nicely printed certificate.
You could get rich fast while sleeping, in that way!
Perhaps the site is even running on some Perl scripts; who knows there might even be a CPAN module in it somewhere.
"If you have four groups working on a compiler, you'll get a 4-pass compiler." - Conway's Law