I was able to get mod_perl2 installed by:
>> yum install perl-devel
>> cpan
>> install YAML
>> install mod_perl2
Then, I configured it thanks to this: http://www.server-world.info/en/note?os=CentOS_6&p=httpd&f=9
I added a new <Directory>
for my web site in case there would be a conflict with plesk.
/cgi-bin
runs regular perl scripts
/mod-perl
runs my scripts using mod_perl2... the $ENV{MOD_PERL} variable does exist here!
@oleg - thanks for your help, a2enmod perl does not work in CentOS
The Perl Support check box in Plesk doesn't seem to have any effect what-so-ever.