I'm guessing you've read perlfaq9 (or a similar example)?

Have you tried omiting the > and < and just using:

print "Window-target: _parent\n\n";
[download]

yet? That might have better results. The example in perlfaq9 does reference <FrameName> in it's example, but I don't believe you should literally use > and <. They are just there to emphasize that you should replace FrameName with your frame's name.

Other than that, it could be a browser issue? That's not standard HTTP (as far as I know), and googling on the topic a bit turns up complaints about that header and IE.

- Matt Riffle