Once all files have been installed, Apache will need to be notified about the new modules. mod_perl may have already done this, however, it is always best to check. Within the file /path/to/apache/conf/httpd.conf, the following will have to be added if it is not already present:
LoadModule perl_module libexec/libperl.so
More can be read on setting up mod_perl further on the mod_perl homepage.