Well, first of all, you're editing the wrong file for Ubuntu. Ubuntu uses a virtual hosts system and you'll want to add the directory section to the file for the virtual host, which will be in the /etc/apache2/sites-available directory. I highly recommend you read the Ubuntu Server Guide on Apache2.

Second is, directory names shouldn't have a trailing slash. Not a big deal, but maybe you would like to see a nice Apache Tutorial to help get the commands right. Also, I'm not sure it matters but I use +ExecCGI rather than ExecCGI.

CGI and mod_perl are very different things. Apache2 on Ubuntu comes with CGI enabled and turned on for /usr/lib/cgi-bin, you can skip all this and just drop your script in that directory.

Setting up mod_perl on Ubuntu isn't difficult but you'll need to install the mod_perl package and then a2enmod it. Search the Ubuntu site, I'm sure they have a guide somewhere.