Apache Reference: mod_perl, PerlSetEnv
Pass a Variable to the SSI/CGI Environment
Syntax: PerlSetEnv variable A
Example: PerlSetEnv FOO_BAR Quux
Since: Apache 1.2
This directive is similar to Apache's standard SetEnv directive;
that is, it sets variable to value inside the SSI/CGI environment.
It differs from SetEnv in that PerlSetEnv is evaluated much
earlier in the HTTP processing, so that variable is
available at an earlier point to Perl modules.