sub major_section { 
   $sec = shift;
   if ( $sec =~ /^([A-Z])$/ ) {
       return ( ord $1 - ord 'A' + 1 );
   } else {
       return 0;
   }
}

##</code><code>##

A.
  1.
  2.
    a.
       1. list data
       2. list data
  3. 
  4.