plpgsql function with more than one array argument

Hi,

thanks for reading this message.

I have a table (in a postgres database) looking like this:
       Table "zdec_bhab"Attribute |   Type    | Modifier
-----------+-----------+----------run       | bigint    |evt       | bigint    |...pcha      | real[]    |...

where pcha is a 2D array, i.e. the first index can go from 1 to some
number and the second is 1..3. 

Now, I'd like to create a plpgsql function taking as an argument 
two vectors (arrays) from pcha:

CREATE FUNCTION mytest(real[],real[]) RETURNS real AS '
DECLARE p1 ALIAS FOR $1; p2 ALIAS FOR $2;
begin
--  RAISE NOTICE ''xxx %'',p2; return p2[1][1];
end;' LANGUAGE 'plpgsql';

I do the following query:

select
pcha[1:1][1:3],pcha[2:2][1:3],mytest(pcha[1:1][1:3],pcha[2:2][1:3]) from
zdec_bhab where nch>=2;  

which yields:                   pcha                     |                   
pcha                     | mytest

---------------------------------------------+---------------------------------------------+--------{{"-21.0788","35.0317","19.2111"}}
        |
 
{{"21.0605","-34.995","-19.2111"}}          |

i.e. mytest seems to return something empty... however, If I uncomment
the RAISE NOTICE
line, I see the correct values (as in the output of the select
statement).

If I do 

select
pcha[1:1][1:3],pcha[2:2][1:3],mytest(pcha[2:2][1:3],pcha[1:1][1:3]) from
zdec_bhab where nch>=2;  

(i.e. the arguments of mytest exchanged), I get the correct values.

Am I doing something wrong or is this a 'feature' ? 
(I'm using  PostgreSQL 7.1.3 on i686-pc-linux-gnu, compiled by GCC
2.95.3).

Is it possible in plpgsql to have functions with more than
one array argument ? What about plperl ?

Or do I have to convert the 2D array into three 1D arrays pcha_x, pcha_y
and pcha_z ?


best regards & thanks for the help,

André