[SemanticForms v1.8.8]

I found it useful in a form to have this syntax in a hidden field:

{{{field|HasDetail|default={{SUBJECTPAGENAME}}_Detail }}}

so I could effectively auto-generate a page name for additional details
linked to a given page without the user being able to alter the name.

To enable this I tweaked SF_FormPrinter.inc, changing line 538 to:

$default_value = $wgParser->replaceVariables($sub_components[1]);

so that it parsed & substituted variable values embedded in the default value clause.