Need help with .htaccess rewrite

Hiyee

I've been googling for a whole day now and can't find a decent
example/guide/howto on the various variables, and functions available
for Rewriting and Redirecting using only a .htaccess file.

I have one host with multiple domain names (it's hosted, so I need to
make changes in the .htaccess file)

The host is domain1.com, and what I'm hoping to achieve is just to
redirect hits to the root of domain2.com to domain2.com/subdir and
still present in the browser as domain2/subdir (At present, hits to
the root of domain2.com present as domain1.com, but domain2.com/subdir
works fine)

All the rewrite rules I've tried either rewrite my entire domain1.com
to domain2.com as well, or don't present in the browser as
domain2.com/subdir, but rather only as domain2.com

And ideas where I can find some decent doc's on writing .htaccess files
as I'm aware I need to do some exclusions to get this working

Thanks

Roy

Thanks for the quick reply Robert

I'm not sure what you mean with internal and external - Both the hosts
are on the same apache server ... (internal, no?)

Could you explain why the www is in brackets, and what the ^ and ?
represent?

Thanks

Roy