Have a hash %config and store things there ($config{ $var } = $value). If you really want them as real variables you'd need to look for "soft references" in perldoc perlref (but you don't really want to do that; use a hash).

Update: Hrmm, I missed the envirnment [sic] part of the title. As someone else mentioned, see perldoc perlvar and look for %ENV.