anchor.diff:  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, $E])],
  +			elements([$c, $C]), elements([$o, $O]), elements([$n, $N]),
  +			elements([$t, $T]), elements([$i, $I]), elements([$n, $N]),
  +			elements([$u, $U]), elements([$e, $E])],
   		list_to_binary(E)).
   
   prop_parse_expect() ->
  
positive.code: 		list_to_binary(T)).
  
  obs_text() ->
  	oneof([128,129,130,131,132,133,134,135,136,137,138,139,140,141,142,143,144,145,
  	146,147,148,149,150,151,152,153,154,155,156,157,158,159,160,161,162,163,
  	164,165,166,167,168,169,170,171,172,173,174,175,176,177,178,179,180,181,
  	182,183,184,185,186,187,188,189,190,191,192,193,194,195,196,197,198,199,
  	200,201,202,203,204,205,206,207,208,209,210,211,212,213,214,215,216,217,
  	218,219,220,221,222,223,224,225,226,227,228,229,230,231,232,233,234,235,
  	236,237,238,239,240,241,242,243,244,245,246,247,248,249,250,251,252,253,
  	254,255]).
  
  qdtext() ->
  	frequency([
  		{99, oneof("\t\s!#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[]^_`abcdefghijklmnopqrstuvwxyz{|}~")},
  		{1, obs_text()}
  	]).
  
  quoted_pair() ->
  	[$\\, frequency([
  		{99, oneof("\t\s!\"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~")},
  		{1, obs_text()}
  	])].
  
  
negative.code: 	]).
  
  langtag_privateuse() -> oneof([[], [$-, langtag_privateuse_nodash()]]).
  langtag_privateuse_nodash() -> [elements([$x, $X]), small_non_empty_list([$-, vector(1, 8, alphanum())])].
  private_language_tag() -> ?LET(T, langtag_privateuse_nodash(), iolist_to_binary(T)).
  
  language_tag() ->
  