IN syntax grammar

query.pp

%skip   space           \s

%token  in              IN
%token  word            \S+

#query:
    in_expression() | text() | unrestricted_text()

#in_expression:
    text() ::in:: field()

#field:
    <word>

#text:
    <word>+

#unrestricted_text:
    ( <word> | <in> )+