nl_tokens: spec may contain nested replacement fields In this case evaluate them using the positional or keyword arguments passed to format ()
pl_tokens: function replace_nested ( name , key ) { if ( / \d+ / . exec ( key ) ) { // If key is numeric, search in positional // arguments return _b_ . tuple . __getitem__ ( $ . $args , parseInt ( key ) ) } else { // Else try in keyword arguments return _b_ . dict . __getitem__ ( $ . $kw , <mask> ) } }