With mod_perl (speed!):
  =======================
  Add this to the mod_perl stuff section in httpd.conf
  [...]
  Alias /otrs-web/ "/opt/otrs/var/httpd/htdocs/"
  Alias /otrs/ "/opt/otrs/bin/cgi-bin/"

  <Location /otrs>
    SetHandler  perl-script
    PerlHandler Apache::Registry
    Options ExecCGI
    PerlSendHeader On
    PerlSetupEnv On
  </Location>

  You may want to use a mod_perl startup script. Compiled modules on startup
  (speed!)! Use the mod_perl startup script which comes with otrs
  (scripts/apache-perl-startup.pl).

  - Change the default startup script location of your httpd to
    $OTRS_HOME/scripts/apache-perl-startup.pl in httpd.conf
    [...]
    # load all otrs modules
    Perlrequire /opt/otrs/scripts/apache-perl-startup.pl
    [...]

  Edit the scripts/apache-perl-startup.pl script:

   - Establish datababase connections on process startup (httpd).

     [...]
     use Apache ();
     use Apache::DBI ();
     Apache::DBI->connect_on_init('DBI:mysql:otrs', 'otrs', 'some-pass');
     # Apache::DBI->connect_on_init($data_source, $username, $auth, \%attr)
     [...]

   - Change the otrs lib dir (if needed)!

     [...]
     # --
     # set otrs lib path!
     # --
     use lib "/path/to/otrs/";