Ripper dose't recognize '__ENCODING__' keyword

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http://pc11.2ch.net/test/read.cgi/tech/1215531152/589

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require ‘ripper’
p Ripper.lex(“puts ENCODING”)

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ruby 1.9.0 (2008-08-26 revision 18849) [i686-linux]

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struct kwtable;
%%
ENCODING, {keyword__ENCODING__, keyword__ENCODING__}, EXPR_END
LINE, {keyword__LINE__, keyword__LINE__}, EXPR_END
FILE, {keyword__FILE__, keyword__FILE__}, EXPR_END
BEGIN, {keyword_BEGIN, keyword_BEGIN}, EXPR_END

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static const struct token_assoc {
int token;
ID *id;
} token_to_eventid[] = {

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{keyword_yield,  &ripper_id_kw},
{keyword__FILE__,  &ripper_id_kw},
{keyword__LINE__,  &ripper_id_kw},
{keyword_BEGIN,  &ripper_id_kw},
{keyword_END,  &ripper_id_kw},
{tAMPER,    &ripper_id_op},

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