get the incoming TCP protocol type

Hi.

Inside a mod_perl2 request handler, how can I find out if the current request was received 
via HTTP or HTTPS ?

I mean :
The client (browser e.g.) gets a URL "http://host.x.y/path1/path2..", and
- translates host.x.y to an IP
- makes a connection to that IP (and port)
- sends a request like :
   GET /path1/path2.. HTTP/1.1
   Host: host.x.y
   ...

OR
The client (browser e.g.) gets a URL "https://host.x.y/path1/path2..", and
- translates host.x.y to an IP
- makes an *SSL* connection to that IP (and port)
- sends a request like :
   GET /path1/path2.. HTTP/1.1
   Host: host.x.y
   ...

and

Inside a handler, I can get
$r->hostname   ==> host.x.y
$r->uri and $r->unparsed_uri  ==> /path1/path2..

and I can also get the port on which the request was received (presumably), via
$r->get_server_port
but that is not really a guarantee, any port could be set for either HTTP or HTTPS.

and then I see
$r->proto and $r->proto_num
but these are relative to the protocol string as it appears in the first request line, not 
to the type of connection that was used for the request.
And in the request, I guess it would always be HTTP/1.1, or ?
(I don't have a HTTPS host right now to check this)

And I haven't really found anything yet in Apache2:RequestRec, Apache2::Connection or 
Apache2::ServerRec which would provide that information.

Is there somewhere a "is_secure()" or something which provides that ?
Or can I rely on the presence/absence of some request header ?

Help..


The point is, I'd like to write the handler once, and use it inside a HTTP or a HTTPS host 
indifferently.  And if possible, I'd also like to avoid having to tell the handler where 
he lives via some PerlSetVar just for that.
But maybe that's the easiest solution ?