Personally I find this works a bit easier, the catch is any special tags like conditionals need to be properly started and ended:
PHP Code:
//just an example
require_once(DIR . '/includes/adminfunctions_template.php');
$findstring = compile_template('<if condition="$show[\'pagenav\']"><td align="$stylevar[right]">$pagenav</td></if>');
$vbulletin->templatecache['SHOWTHREAD'] = str_replace($findstring, $vbulletin->templatecache['strike_center_edit'] . $findstring, $vbulletin->templatecache['SHOWTHREAD']);
Sticks one template's contents into a specific place of another one