本模板用于检测替换引用.
在模板源代码中加入<includeonly>{{subst:</includeonly>substcheck<includeonly>}}</includeonly>。在渲染时,这段代码会展开为:
<includeonly>{{subst:</includeonly>substcheck<includeonly>}}</includeonly>
SUBST
substcheck
{{subst:substcheck}}