If you want to POST the data, you will need to generate a form to do it, and with the help of some javascript *ducks* you can make it autosubmit.

sub paypal_redirect {
       my ($query, $total_cost) = @_;
       my $cgi = CGI->new;
       print $cgi->header;      # normal header
       print $cgi->start_form(-method => 'post', 
                              -action=>'https://www.paypal.com/cgi-bin
+/webscr');
       print $cgi->hidden(-name => '_cmd', -value => '_xclick');
       print $cgi->hidden(-name => 'business', -value => $email);
       print $cgi->hidden(-name => 'item_name', -value => $comment);
       print $cgi->hidden(-name => 'item_number', -value => $query->pa
+ram('session'));
       print $cgi->hidden(-name => 'amount', -value => $total_cost);
       print $cgi->hidden(-name => 'no_note', -value => 1);
       print $cgi->hidden(-name => 'currency_code', -value => 'USD');
       print $cgi->submit('Continue to PayPal'); # you will need that 
+button in case
                                                 # the user has JS off
+.
       print $cgi->end_form;

       print <<JS;
       <script language="JavaScript">
       <!--
           document.forms[0].submit();
       //-->
       </script>
JS
       
       
}
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