simplevars = oldstyle updateable content

   <!--mksite:simplevars--> 
   <!--mksite:nosimplevars--> 
   <!--mksite:warnsimplevars--> 

The option can be selected in the sitefile, per default we do update content prefixed with these comment variables and additionally warn on those expansions. The simplevars expansion is highly depracated and subject to be removed in the future. It is a heritage of earlier mksite.sh generations where it was the only variable expansion variant. Therefore we default to warnsimplevars that expands them but warns about it.

   input: derived <!--varname-->2004/04 FOO
  output: derived 2004-04-16 FOO
 default: derived 2004/04 FOO

   input: derived <!--varname?-->2004/04 FOO
  output: derived - 2004-0416 FOO
  output: derived (2004-0416) FOO
 default: derived  2004/04 FOO

Note how a single word is updated with this variable expansion. Over time we included a set of wordchars to update atleast default text content with simple date formatting or simple filename formatting.

For the variable expansion we always use the edited variant value as we did describe it in expandvars. Anyway, do not use this expansion mechanisms - fix any instance that you will be warned about and add an explicit
<!--mksite:nosimplevars--> to your sitefile.