Notice that the two symbols must be distinct. The header prefix to be inserted before a new letter begins. The flag indicating the condition of inserting new letter header. Default is 0, which means no header. Positive means insert an uppercase letter between prefix and suffix.
Negative means insert a lowercase letter.
The command to be inserted between two level 2 items. The command to be inserted between a level 0 item and a level 1 item. The difference between this and previous is that in this case the level 0 item doesn't have any page numbers. The command to be inserted between a level 1 item and a level 2 item. The command to be inserted between a level 1 item and a level 2 item.