anchor.diff:  rebind_op -> '/='  : '$1'.
   rebind_op -> '**=' : '$1'.
   
  +%% Boolean operators
  +bool_op -> 'and' : '$1'.
  +bool_op -> 'or'  : '$1'.
  +
   %% Comparison operators
   comp_op -> '===' : '$1'.
   comp_op -> '==' : '$1'.
  
positive.code:   exprs
    expr
    match_expr
    comp_expr
    range_expr
    add_expr
  
negative.code: dict -> '{' '}' :                #dict{line=?line('$1'), elements=[]}.
  dict -> '{' dict_entries '}' :   #dict{line=?line('$1'), elements='$2'}.
  
  dict_entries -> bool_expr '=>' expr : [{'$1','$3'}]. % FIXME: change add_expr to 1 below match
  dict_entries -> bool_expr '=>' expr ',' dict_entries : [{'$1','$3'}|'$5'].
  
  Erlang code.
  
  