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   <S>                   ::= <syntax>
   <syntax>              ::= <rule> | <rule> <syntax>
   <rule>                ::= <opt-whitespace> "<" <rule-name> ">" <opt-whitespace> "::=" <opt-whitespace> <expression> <line-end> <reduction-code>
   <opt-whitespace>      ::= " " <opt-whitespace> | ""  
   <expression>          ::= <list> | <list> <opt-whitespace> "|" <opt-whitespace> <expression>
   <line-end>            ::= <opt-whitespace> <EOL> | <line-end> <line-end>
   <list>                ::= <term> | <term> <opt-whitespace> <list>
   <term>                ::= <named-term> | <unnamed-term>
   <named-term>          ::= <unnamed-term> <opt-whitespace> "(" <unquoted-text> ")"
   <unnamed-term>        ::= <literal> | "<" <rule-name> ">" | '""'
   <literal>             ::= '"' <double-quoted-text> '"' | "'" <single-quoted-text> "'"
   <double-quoted-text>  ::= <quoted-text-part> | "'" | <double-quoted-text> <quoted-text-part> | <double-quoted-text> "'"
   <single-quoted-text>  ::= <quoted-text-part> | '"' | <single-quoted-text> <quoted-text-part> | <single-quoted-text> '"'
   <quoted-text-part>    ::= "(" | ")" | "<" | ">" | "::=" | " " | '""' | "|" | <text-terminal> | <quoted-character>
   <rule-name>           ::= <unquoted-text>
   <unquoted-text>       ::= <text-terminal> | <quoted-character> | <unquoted-text> <text-terminal> | <unquoted-text> <quoted-character>
   <reduction-code>      ::= "<<<" <line-end> <reduction-code-text> <EOL> ">>>" <line-end> | ""
   <reduction-code-text> ::= <reduction-code-text-part>
   <reduction-code-text> ::= <reduction-code-text-part> <reduction-code-text>
   <reduction-code-text-part> ::= "<<<" | ">>>" | '"' | "'" | "(" | ")" | "<" | ">" | "::=" | " " | '""' | "|" | <text-terminal> | <quoted-character>