if (defined $ENV{'QUERY_STRING'}) {
    # assign to variable
    # check for login parameter
}

##</code><code>##

use CGI;
my $q = CGI->new();

my $age = $q->param('age');
my $login = $q->param('login');

if ($age) {
    # do whatever
}

if ($login) {
    # do whatever
}