Prompt command in PLSQL code

Question

Hi,
In the below script giving the ability to the user to continue or Exit from the script execution.
Calling this script from a batchfile. Seems Y option is working but even "N" executing the script.
test.sql
prompt Do you want to continue script execution?
accept odg prompt 'Y / N :  ';
set termout off;
set verify off;
set heading off;
set pause off;
set echo off;
column a newline;
select decode(upper('&odg'), 'Y', 'prompt Executing ...',
                                  'prompt Stopped'
       decode(upper('&odg'), 'Y', '', 'accept return_key prompt ''Press <Return>''') a,
       decode(upper('&odg'), 'Y', '', 'exit') a
from dual;
set termout on;
SET FEEDBACK OFF
SET VERIFY OFF
SET SERVEROUTPUT ON
DECLARE
   lc_file_handle        UTL_FILE.file_type;
   lc_file_dir           VARCHAR2 (100);
   lc_file_name          VARCHAR2 (50);
   data                VARCHAR2 (500);
   v1                    ECCSYS.hwcontainer.hwcontainerserialnumber%type;
   v2                    ECCSYS.storagedevice.devicename%type;
   s2                    ECCSYS.storagedevice.isreserved%type;
   D1                SYS.DBA_DIRECTORIES.DIRECTORY_PATH%type;           
BEGIN  
SELECT DIRECTORY_PATH INTO D1 FROM SYS.DBA_DIRECTORIES WHERE DIRECTORY_NAME ='DATA_PUMP_DIR';
   lc_file_dir := 'DATA_PUMP_DIR';
   lc_file_name := '&1';
   lc_file_handle := UTL_FILE.fopen (lc_file_dir, lc_file_name, 'R');
   LOOP
      BEGIN
         UTL_FILE.get_line (lc_file_handle, data);
     v1 := SUBSTR (data,1,INSTR (data, ',', 1) - 1);
     v2 := substr(data, INSTR (data, ',', 1, 1) + 1, length(data) - INSTR (data,',', 1, 1));
       select isreserved into s2 from ECCSYS.storagedevice where devicename=v2 and storagearrayid = (select hwcontainerid from ECCSYS.hwcontainer where hwcontainerserialnumber =v1);
     DBMS_OUTPUT.PUT_LINE(v1 ||' '|| v2 ||' '|| s2);
      EXCEPTION
         WHEN NO_DATA_FOUND
         THEN
            EXIT;
      END;
   END LOOP;
EXCEPTION
   WHEN OTHERS
   THEN
      DBMS_OUTPUT.PUT_LINE('Please put the file ' || lc_file_name || ' into location :' || D1);
      UTL_FILE.fclose (lc_file_handle);
END;
accept return_key prompt 'Press <Return>'
EXIT;O/P
C:\ECC\Repository\admin\rambdb\dpdump>test.bat
Enter FILE NAME: test.txt
test.txt
SQL*Plus: Release 11.2.0.3.0 Production on Thu Apr 18 01:05:19 2013
Copyright (c) 1982, 2011, Oracle.  All rights reserved.
Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - Production
With the Partitioning and OLAP options
Do you want to continue script execution?
Y / N :  N
000190300153 170 0
000190300153 171 0
Press <Return>
Disconnected from Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - Production
With the Partitioning and OLAP options
C:\ECC\Repository\admin\rambdb\dpdump>

Answer 1

I don't see how this part would work:
select decode(upper('&odg'), 'Y', 'prompt Executing ...',
                                  'prompt Stopped'
       decode(upper('&odg'), 'Y', '', 'accept return_key prompt ''Press <Return>''') a,
       decode(upper('&odg'), 'Y', '', 'exit') a
from dual;If the user input is other than Y, this query would return the text
'prompt Stopped', 'accept return_key prompt ''Press <Return>'', 'exit'
But these are text strings, not actual code that is executed.