As someone here pointed out in an off-list email (thanks!), I had forgotten to load the perl module, by writing PerlModule MyRoot::Testing in httpd.conf. That wasn't very clever...
But then it still didn't work, until for some reason I changed PerlAuthenHandler MyRoot::Testing->autologin to PerlAuthenHandler MyRoot::Testing::autologin It's doing my head in, as in the line above this one, a -> is used without any problems. It's all not very important, but I'd like to write code of which I understand why it works, rather than code that just happens to work. Martijn.