What 3 elements? I'm completely guessing, but maybe its cause GRAMPROG expands to 
$1       $2    $3        $4       $5      ...                  
%token <ival> GRAMPROG GRAMEXPR GRAMBLOCK GRAMBARESTMT  ...
or
                  $1       $2    $3        $4

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I just stumbled upon Perl 5 Internals by Simon Cozens which talks a bit this in Chapter 5. The Lexer and the Parser

In reply to Re: Where does $4 come from here? by Anonymous Monk
in thread Where does $4 come from here? by PerlOnTheWay

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