.htaccess regular expressions

Apparently, this doesn't work the way I thought it would.

RewriteRule ^([a-z]+)[\Z/] pre-$1.ext?

I want both examples to work like this:

1. /prog  -> pre-prog.ext?
2. /prog/ -> pre-prog.ext?

Am I going to have to bite the bullet and write two separate lines?

>>2
No, that's all wrong.

/prog
and
/prog/stuff

Are supposed to be

pre-prog.ext?
and
pre-prog.ext?stuff

Did you see the fucking \Z ?

Forget it, you suck and I'm doing something else now.