my $arrayRef;
   if ( defined ?attr1Hash{$attr1}){
      my $key ="attr1.attr2.attr3";
      $arrayRef = $fullHash{$key};
   } 
   if ( defined $arrayRef){
      ...
   }

##</code><code>##

   my $arrayRef;
   my $key ="attr1.attr2.attr3";
   $arrayRef = $fullHash{$key};
   if ( defined $arrayRef){
      ...
   }


##</code><code>##

    $EventHash{$pid} = [ create_ts, last_upt, $ev_cnt];