그런경우 다음처럼 시도해볼수 있을것 같습니다.
<div>
<?php
ob_start();
include_once(G5_BBS_PATH . '/list.php');
$list_in_view = ob_get_clean();
$listonly_in_view = [];
preg_match('!<div class="tbl_head01 tbl_wrap">\s*<table>.*?</table>\s*</div>!s', $list_in_view, $listonly_in_view);
if (count($listonly_in_view) == 1) {
echo $listonly_in_view[0];
}
?>
</div>