select * from the_table where '10.0.4.30'::inet <<= ANY (string_to_array(b, '|')::inet[]);

create type blablabla as (
   a int,
   b inet
);
create function to_table() returns setof blablabla $$
declare _rec record;
_ar text[];
_r2 blablabla;
_i int;
begin
 for _rec in select * from the_table loop
   _ar := string_to_array(_rec.b, '|');
  _r2.a := _rec.a;
    for _i in array_lower(_ar)..array_upper(_ar) loop
        _r2.b := _ar[i];
        return next _r2;
   end loop;
 end loop;
 return;
end$$ language 'plpgsql';