problem with function in plpgsql

Hello;
I have a table pz like this :
Table    = pz
+----------------------------------+----------------------------------+-------+

|              Field               |              Type                |
Length|
+----------------------------------+----------------------------------+-------+

| cle                              | int4 not null
|     4 |
| titre                            | varchar() not null
|    25 |
| typ                              | char() not null
|     1 |
| in_unit                          | int4 not null
|     4 |
| out_unit                         | int4 not null
|     4 |
| pcterr                           | float8
|     8 |
| a0                               | float8
|     8 |
| af                               | float8
|     8 |
| desctype                         | varchar()
|     4 |
| description                      | int8
|     8 |
+----------------------------------+----------------------------------+-------+

I have to create a function who take me one row like that
 create function test_exist_pz (text,int4,int4,float,float) returns text
as '
declare
  pzrec pz%RowType;
begin
  select * into pzrec
   from pz
   where typ = $1
     and in_unit = $2
     and out_unit = $3
     and A0 = $4
     and AF = $5;
  if not found then
    pzrec.cle = -1;
  end if;
  return pzrec;
end;
' language 'plpgsql';
CREATE
When I try to work with the function it doesn't I have this result :
seed=> select test_exist_pz('a',1,1,1.1,1.2);
ERROR:  attribute 'pzrec' not found
I am not very familiar with plpgsql and so if there is somebody
who can help me or if thre is somebody who can say where can
I find documentation about plpgsql it is very well

Thanks


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