anchor.diff:  	]).
   
   langtag_privateuse() -> oneof([[], [$-, langtag_privateuse_nodash()]]).
  -langtag_privateuse_nodash() -> [oneof([$x, $X]), small_non_empty_list([$-, vector(1, 8, alphanum())])].
  +langtag_privateuse_nodash() -> [elements([$x, $X]), small_non_empty_list([$-, vector(1, 8, alphanum())])].
   private_language_tag() -> ?LET(T, langtag_privateuse_nodash(), iolist_to_binary(T)).
   
   language_tag() ->
  
positive.code: expect() ->
  	?LET(E,
  		[$1, $0, $0, $-,
  			oneof([$c, $C]), oneof([$o, $O]), oneof([$n, $N]),
  			oneof([$t, $T]), oneof([$i, $I]), oneof([$n, $N]),
  			oneof([$u, $U]), oneof([$e, $E])],
  		list_to_binary(E)).
  
  prop_parse_expect() ->
  
negative.code: 		list_to_binary(T)).
  
  obs_text() ->
  	choose(128, 255).
  
  qdtext() ->
  	frequency([
  		{99, elements("\t\s!#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[]^_`abcdefghijklmnopqrstuvwxyz{|}~")},
  		{1, obs_text()}
  	]).
  
  quoted_pair() ->
  	[$\\, frequency([
  		{99, elements("\t\s!\"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~")},
  		{1, obs_text()}
  	])].
  
  