In addition to the already mentioned new features in mod_perl 2.0, the following are of major importance:
Apache 2.0 protocol modules are supported. Later we will see an example of a protocol module running on top of mod_perl 2.0.
mod_perl 2.0 provides a very simple-to-use interface to the Apache filtering API; this is of great interest because in mod_perl 1.0 the Apache::Filter and Apache::OutputChain modules, used for filtering, had to go to great lengths to implement filtering and couldn't be used for filtering output generated by non-Perl modules. Moreover, incoming-stream filtering has now become possible. We will discuss filtering and see a few examples later on.
A feature-full and flexible Apache::Test framework was developed especially for mod_perl testing. While intended to test the core mod_perl features, it is also used by third-party module writers to easily test their modules. Moreover, Apache::Test was adopted by Apache and is currently used to test the Apache 1.3, 2.0, and other ASF projects. Anything that runs on top of Apache can be tested with Apache::Test, whether the target is written in Perl, C, PHP, etc.
The support of the new MPMs makes mod_perl 2.0 able to scale better on a wider range of platforms. For example, if you've happened to try mod_perl 1.0 on Win32 you probably know that parallel requests had to be serialized—i.e., only a single request could be processed at a time, rendering the Win32 platform unusable with mod_perl as a heavy production service. Thanks to the new Apache MPM design, mod_perl 2.0 can now efficiently process parallel requests on Win32 platforms (using its native win32 MPM).