2.6. Instant Modules with Apache::Registry
By now, although it may not be obvious, you've seen two of the problems with using the Apache APIs. The first problem is that you can't make changes to modules casually. When using the Perl API, you have to restart the server in order to have your changes take effect. With the C API, you have to rebuild the module library or completely relink the server executable. Depending on the context, this can be a minor annoyance (when you're developing a module on a test server that gets light usage) to a bit of a headache (when you're trying to apply bug fixes to an installed module on a heavily used production server).
The second problem is that Apache API modules don't look anything like CGI scripts. If you've got a lot of CGI scripts that you want to run faster, porting them to the Apache API can be a major undertaking.
Apache::Registry, an Apache Perl module that is part of the mod_perl distribution, solves both problems with one stroke. When it runs, it creates a pseudo-CGI environment that so exactly mimics the real thing that Perl CGI scripts can run under it unmodified. It also maintains a cache of the scripts under its control. When you make a change to a script, Apache::Registry notices that the script's modification date has been updated and recompiles the script, making the changes take effect immediately without a server restart. Apache::Registry provides a clean upgrade path for existing CGI scripts. Running CGI scripts under ...