Just generate a redirection header, as documented in the CGI Manpage.

#!/usr/bin/perl -w
use strict;
use CGI;

my $query = new CGI;
my $url = $query->param("whatever");

### log the url to a file, database or whatever

### redirect user
print $query->redirect(-uri=>$url,
                       -nph=>1);
[download]

hope to help

update: oops, forgot to use CGI :)
snowcrash //////