Nonexistent NEW relation in some places of rules

In general, the task I'm trying to solve is to make a multiply inserts
for a table on the one only insert for a view.  It should be noted
about the method of producing these multiply rows, that they depend on
the VALUES given to that <top level> INSERT.  So, the trivialized
schema is:


create function produce (text) returns setof text
language plpgsql
as '
begin   return next $1||1;   return next $1||2;   return next $1||3;   return;
end;
';

create table a (a text);

create view b as   select a as b   from a;

create rule b as   on insert to b do instead   insert into a   select * from produce (new.b);


And I get
       psql:zhoppa.sql:21: ERROR:  Relation "*NEW*" does not exist

when I feed this to psql...

So, what is wrong in using NEW right from the FROM?

Thanks in advance.