use CGI;
my $q = new CGI;
print $q->header(-target=>'ResultsWindow');

# or roll your own header like this 
print "Window-Target: ResultsWindow
Content-Type: text/html\n\n";

##</code><code>##

<a href="/cgi-bin/script.pl?target=SomeFrame&other=stuff">Click Here</a>

# and in the script
my $target = $q->param('target');
print $q->header(-target => $target );