=head1 Upgrading to Catalyst 5.9
The major change is that L<Plack>, a toolkit for using the L<PSGI>
-stack, now replaces most of the subclasses of L<Catalyst::Engine>. If
+specification, now replaces most of the subclasses of L<Catalyst::Engine>. If
you are using one of the standard subclasses of L<Catalyst::Engine> this
should be a straightforward upgrade for you. It was a design goal for
this release to preserve as much backwards compatibility as possible.
=head2 Upgrading the mod_perl / Apache Engines
The engines that are built upon the various iterations of mod_perl,
-L<Catalyst::Engine::Apache::MP13> and L<Catalyst::Engine::Apache2::MP20>,
-should be seamless upgrades and will work using using
-L<Plack::Handler::Apache1> or L<Plack::Handler::Apache2> as required.
+L<Catalyst::Engine::Apache::MP13> (for mod_perl 1, and Apache 1.x) and
+L<Catalyst::Engine::Apache2::MP20> (for mod_perl 2, and Apache 2.x),
+should be seamless upgrades and will work using using L<Plack::Handler::Apache1>
+or L<Plack::Handler::Apache2> as required.
L<Catalyst::Engine::Apache2::MP19>, however, is no longer supported, as
-Plack does not support mod_perl version 1.99
+Plack does not support mod_perl version 1.99. This is unlikely to be a
+problem for anyone, as 1.99 was a brief beta-test release for mod_perl
+2, and all users of mod_perl 1.99 are encouraged to upgrade to a
+supported release of Apache 2 and mod_perl 2.
=head2 Upgrading the HTTP Engine