The ''transclusion'' variable is set automatically by the transclude widget to contain a string that identifies the position of the current node within the widget tree. In the sidebar it is set to `{|$:/core/ui/PageTemplate/sidebar|||}` and within the tiddler "HelloThere" in the story river it is set to `{HelloThere|HelloThere|||}`. Each nested level of transclusion appends another curly bracketed list of symbols.
The QualifyMacro uses the ''transclusion'' variable to identify the stack of transcluded tiddlers.