my @words = split /\s+/,$keyword;
my @list;
my $where = join(' OR ',
    map { 
        my $col = $_; 
        map { push @list, "%$_%"; "$col like ?" } @words
    } qw(mfg productID desc)
);
my $sth = $dbh->prepare('SELECT * FROM productTable WHERE ' . $where);
$sth->execute(@list);