RT-Extension-CommandByMail 0.9 Not processing commands in RT 3.6.7 (Plugins problems?)

While I wait on ubuntu to release RT 4 (I assume I can go from 3.6.7
straight to 4; I could be wrong here), which would hopefully take care
of https://bugs.launchpad.net/ubuntu/+source/request-tracker3.8/+bug/444046,
I am testing RT-Extension-CommandByMail 0.9 in 3.6.7. Before you ask,
no I can’t just download RT from best practical; I have to deal with
packages provided by ubuntu.

So, the first question is how do I set those plugins up? Having

Set(@MailPlugins, qw(
Auth::MailFrom
Filter::TakeAction
));
Set(@Plugins, qw(
RT::Extension::CommandByMail
));

In RT_SiteConfig.pm seem to do nothing, but at least causes no harm
(cheerfully ignored). Reading
http://comments.gmane.org/gmane.comp.bug-tracking.request-tracker.user/59470,
I also tried

use Auth::MailFrom;
use Filter::TakeAction
use RT::Extension::CommandByMail;

which caused RT not to start. What else should I try?

While I wait on ubuntu to release RT 4 (I assume I can go from 3.6.7
straight to 4; I could be wrong here), which would hopefully take care
of https://bugs.launchpad.net/ubuntu/+source/request-tracker3.8/+bug/444046,
I am testing RT-Extension-CommandByMail 0.9 in 3.6.7. Before you ask,
no I can’t just download RT from best practical; I have to deal with
packages provided by ubuntu.

So, the first question is how do I set those plugins up? Having

Set(@MailPlugins, qw(
Auth::MailFrom
Filter::TakeAction
));
Set(@Plugins, qw(
RT::Extension::CommandByMail
));

In RT_SiteConfig.pm seem to do nothing, but at least causes no harm
(cheerfully ignored). Reading
http://comments.gmane.org/gmane.comp.bug-tracking.request-tracker.user/59470,
I also tried

use Auth::MailFrom;
use Filter::TakeAction
use RT::Extension::CommandByMail;

which caused RT not to start. What else should I try?

  BTW, here is my RT_SiteConfig.pm file showing the different

attemps to include the plugins.

RT_SiteConfig.pm (3.22 KB)