package X;
use CGI;  
$q = CGI->new;
package Y;
use CGI;  
$r = CGI->new;

print $X::q->param('a'), " = ", $r->param('a');

##</code><code>##

friday:~ $ perl cgi
(offline mode: enter name=value pairs on standard input)
a=123
=
123 = 123