Any Perl code in Apache configuration files should be placed between <Perl> and </Perl> directives. This code can define variables and lists used by mod_perl to assign the associated Apache configuration directives; for example, assigning the $ServerAdmin variable will redefine the ServerAdmin Apache configuration directive.

Suppose you share the same Apache configuration files across multiple servers, and you want to allow personal directories on only one of them. You can use Perl directives like this:

<Perl>
if ('hostname' =~ /public/) {
        $UserDir = "public.html";
} else {
        $UserDir = "DISABLED";
}
1;
</Perl>

Directive blocks (such as <Location>...</Location>) can be represented as a hash. For example:

<Perl>
$Location{"/design_dept/"} = {
        DefaultType   => 'image/gif',
        FancyIndexing => 'On'
}
</Perl>

11.5. Server-Side Includes with mod_perl		11.7. Apache:: Modules