$i = 0;
$open = 0;

foreach (@images)
# or: while ($sth->fetch)
# or: while (readdir(IMAGE_DIR))
{
   (print "<tr>", $open = 1) unless $open;
   print "<td>";
   # print image
   print "</td>"
   (print "</tr>", $open = 0) unless ++$i % 5;
}

print "<tr>" if $open;