#!/usr/bin/perl -wT

use CGI;
use CGI::Carp qw(fatalsToBrowser);
use DBI;

use strict;
use warnings;

...

    my $sth = $dbh->prepare(qq{UPDATE $regtable SET favorites=? WHERE ID=?});
    $sth->execute($favorites, $ID) or die $dbh->errstr;

...