{{#invoke:TEMPLATENAME|main}}

This module returns the name of the page it is being transcluded from. This differs from {{FULLPAGENAME}}, which returns the name of the currently viewed page even if it is called from a template. To use this /doc subpage as an example, if you are viewing the main module page, {{#invoke:TEMPLATENAME|main}} should generate Module:TEMPLATENAME/doc while {{FULLPAGENAME}} should generate Module:TEMPLATENAME/doc.

To get the same behavior for variables other than {{FULLPAGENAME}}, this module can be passed as a parameter to their corollary parser functions as in: {{PAGENAME:{{#invoke:TEMPLATENAME|main}}}} → TEMPLATENAME/doc.