From Annie Hall's GardenDesigns.com

$EnablePageListProtect

When set to 1 (which is the default), causes (:pagelist:) and (:searchresults:) to exclude listing any pages for which the browser does not currently have read authorization. Setting this to zero means that read-protected pages can appear in a listing, but can also speed up searches considerably (because page permissions do not need to be checked).

$SearchPatterns

An array of page name patterns to be required or excluded from search and pagelist results. In order to be included in a search listing or page listing, a page's name must not match any pattern that is delimited by exclamation points (!) and must match all other patterns. See Cookbook:SearchPatterns.

# Limit all searches to Main group
$SearchPatterns['default'][] = '/^Main\\./';
# Exclude the Main group from search results
$SearchPatterns['default'][] = '!^Main\\.!';
# Exclude RecentChanges pages from search results
$SearchPatterns['default'][] = '!\\.(All)?RecentChanges$!';
# Prevent a page from listing itself in (:pagelist:) or (:searchresults:)
$SearchPatterns['default'][] = FmtPageName('!^$FullName$!', $pagename);

$SearchBoxOpt

For example $SearchBoxOpt ['target'] = '$DefaultGroup.Search';

$EnablePageIndex

When set to 1, causes Pm Wiki to maintain a "link and word index" in $PageIndexFile which significantly speeds up categories, backlinks, and searches.

$PageIndexFile

The location of the "page index" file for (:pagelist:), defaults to $WorkDir/.pageindex.

$PageListCacheDir

The name of a writable directory where Pm Wiki can cache results of (:pagelist:) directives to speed up subsequent displays of the same list. Default is empty, which disables the pagelist cache.

# Enable pagelist caching in work.d/
$PageListCacheDir = 'work.d/';

$PageSearchForm

The page to be used to format search results for ?action=search (unless the current page has a "searchresults" directive in it). This variable can be an array, in which case the first page found from the array is used.

# Use Search page in current group if it exists, otherwise use Site.Search
$PageSearchForm = array('$Group.Search', '[=$[$SiteGroup/Search]=]');

$FPLTemplatePageFmt

The pages to be searched for a pagelist template specified by a fmt=#xyz parameter. Defaults to searching the current page, Site.LocalTemplates? and Site.PageListTemplates.

# PMWiki default setup
global $FPLTemplatePageFmt;
$FPLTemplatePageFmt = array(
    '{$FullName}', 
    '{$SiteGroup}.LocalTemplates', 
    '{$SiteGroup}.PageListTemplates');

# Search a Group.Templates page as well as the Site templates
global $FPLTemplatePageFmt;
$FPLTemplatePageFmt = array(
    '{$Group}.Templates',
    '{$SiteGroup}.LocalTemplates',
    '{$SiteGroup}.PageListTemplates');

# Search a Group.Templates page as well as the Site templates
global $FPLTemplatePageFmt;
SDV($FPLTemplatePageFmt, array('{$FullName}',
    '{$Group}.Templates',
    '{$SiteGroup}.LocalTemplates', '{$SiteGroup}.PageListTemplates')
   );

$EnableUndefinedTemplateVars

This variable controls how undefined {$$Variable} is processed in includes and PageList templates. If set to 0 (default), undefined {$$Variable}s are removed from the included section or template. If set to 1, undefined {$$Variable}s are displayed as is, with {$$...}. Note that Pm Wiki versions 2.2.13 and earlier kept unset include/template variables.

$EnableUndefinedTemplateVars = 0; # Delete unset raw template variables

$EnableUndefinedTemplateVars = 1; # Keep and print unset raw template variables