[erlang-questions] merl behaves differently (incorrectly?) in OTP 21

[John Doe]

minimal code for reproducing the issue

-module(a).
-export([test/0]).
-include_lib("syntax_tools/include/merl.hrl").
test() ->
        Str = "a_string",
        ?Q("_@REDACTED@ -> 1").

Result in OTP 19:

{tree,clause,
      {attr,7,[],none},
      {clause,[{tree,string,{attr,0,[],none},"a_string"}],
              none,
              [{integer,7,1}]}}

in OTP 21

{tree,clause,
      {attr,7,[],none},
      {clause,[{tree,class_qualifier,
                     {attr,0,[],none},
                     {class_qualifier,{atom,7,throw},
                                      {tree,string,{attr,0,[],none},"a_string"},
                                      {var,7,'_'}}}],
              none,
              [{integer,7,1}]}}
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