HTTP auth can be implemented in Perl too, but CPAN seems to have a dearth of modules to do it for you. (There are some for Catalyst and Plack, but not classic CGI.)

Right, because classic CGI ( as in mod_cgi, http://tools.ietf.org/html/rfc3875 ) , doesn't provide for external programs to perform authentication (it will strip any Www-authenticate headers) -- its a limitation of CGI

You can work around it in apache by

compile Apache with -DSECURITY_HOLE_PASS_AUTHORIZATION option,

use mod_rewrite to pass the Authorization header to the application with the rewrite rule like following (see Plack::Middleware::Auth::Basic)

use mod_perl

use fastcgi configured with "-pass-header HTTP_AUTHORIZATION "