The easiest way to do this isn't (really) a Perl solution at all: use HTML frames to mask the URI within your index page.

Something like the following (HTML) would do the trick:

<FRAMESET ROWS="0, *" FRAMEBORDER=0>
<FRAME NORESIZE />
<FRAME NAME=CONTENT SRC="http://www.yahoo.com" NORESIZE />
</FRAMESET>
[download]

This will display the www.yahoo.com page, but display the URI of the page that contains the frameset.

The CGI module supports the output of frames, and hence could be used to do this from within a script.

Hope that helps.

-- Foxcub
#include www.liquidfusion.org.uk

Update: Clarifications.