meta
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The formal definition is divided into four levels. The bot-
tom level describes the meta-notation used in this document. The
second level describes basic lexical analyzers that feed tokens
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These rules show a field meta-syntax, without regard for the
particular type or internal syntax. Their purpose is to permit
detection of fields; also, they present to higher-level parsers
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The meta-construct of prefacing field names with the string
"Resent-" has been added, to indicate that a message has been
forwarded by an intermediate recipient.
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