The latest version of mod_perl2 is recommended, and can be downloaded from http://perl.apache.org/download/index.html
Evergreen was built using a pretty vanilla build of Mod_Perl. Make and install mod_perl2 by executing the following command
perl Makefile.PL MP_AP_PREFIX=/opt/ make make install
Add to the Apache config (httpd.conf usually):
LoadModule perl_module modules/mod_perl.so
See the mod_perl documentation for more complex installations.