PLS-00363: expression '0' cannot be used as an assignment target

[LKBrwn_DBA]

Try this:

TargetInstance=""
SourceInstance=""
Rerun="N"
ReturnStatus=`
sqlplus -s /nolog << !EOF >> $LOG 2>&1
set serveroutput on size 1000000
whenever sqlerror exit sql.sqlcode
connect apps/$PWD
declare
l_return_status number := 0;
begin
  CLONE_SETUP.clone_main('$TargetInstance','$SourceInstance','$Rerun',l_return_status);
  dbms_output.put_line(l_return_status);
  if l_return_status = 0 then
    commit;
  else
    rollback;
  end if;
end;
/
exit
!EOF`
if [ $ReturnStatus -eq 0 ]; then
  echo 'Rapid Clone succeeded, Commit performed'
else 
  echo 'Rapid Clone failed, Rollback performed'
fi
exit