I would go as far as claiming that what's in the parens itself in that case is yet another minilanguage (very closely related to Perl itself: it consists of exactly three Perl statements!) that does not fit in other parts of Perl's syntax, and thus a very special case: of course Perl 6 knows better and gives it an entirely different name which IIRC is C<loop> and not by chance takes one letter more wrt "for" since that's for huffmanization and in fact it is thought to be on a much sparser basis to begin with.

• I won't deny Perl 6 gives it a different name, but the Perl 5 parser already knows the 'loop' construct. perly.y has a token 'loop' under which all loop, including the bare block and 4 (!) 'for' constructs. (for my $v (), for $v (), for (), are all parsed separately).
• The C-style for loop doesn't have three statements inside the parens, it has three expressions - each of which may be empty.
• Each of the expressions is a different kind of expression (first introduces a scope, second is a boolean expression, third may introduce a scope), but they do fit in other parts of Perls syntax. Of course, you are right in the sense that 'for (;;)' is the only place that requires exactly three expressions.
• I don't understand the huffmanization remark. Huffmanization means you're minimizing the length of the average program, using tokens that are never a prefix of another token. Making little used tokens longer makes sense, but only if you either the freed up token for something that's used more often, or if the freed token is a prefix of some other token that cannot be replaced. So, what keyword starting with 'for' is used in Perl6? Surely you aren't saying in Perl6 'format' is going to be used more often than 'loop'? ;-)