How do I make mod_rewrite.c work with mod_perl.c?

Question

Basically I want to do this:

RewriteCond %{QUERY_STRING} (^|&)t=
RewriteRule .* - [E=tag:name]

But the E only works with CGI ,I need to use something like this to work in mod_perl:

PerlSetEnv TEMPLATE_PATH /usr/share/templates

I want to set it only if the querystring matches something,how to do that kind of settings?