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: Terminals
    eol '(' ')' '[' ']' '{' '}'
    float integer string atom regexp true false nil 
    identifier punctuated_identifier erl
    '+' '-' '*' '/' '%' '**' ',' '.' '..' '=' '=>' '$' ':'
    '===' '==' '!=' '>' '<' '>=' '<='
    '+=' '-=' '*=' '/=' '**='
  
negative.code:   exprs
    expr
    match_expr
    bool_expr
    comp_expr
    range_expr
    add_expr
  