Re: $msg->sender bug? Or bad usage?

* Adam Augustine ([email protected]) [040121 01:22]:
> I have a script that catches bounces from a mailing list. Some of the 
> bounces are very, very odd which tend to tickle bugs in my code.

code:

> @from = $msg->sender;
> print "\$#from is: $#from\n";
> print "\$from is: $from[0]\n";

output:

> $#from is: 0
> Use of uninitialized value in concatenation (.) or string at 
> ./testscript.pl line 11, <STDIN> line 1.
> $from is:

> My understanding is that if an array is empty then $#array should be -1. 
> It seems to me that @from = $msg->sender; seems to be doing something 
> very strange to @from, making all values none-existent, but changing the 
> index.

The answer is simple, but sometimes we get blinded when we focus too
much on what we expect.  $msg->from, ->to, ->cc, and ->bcc all return
lists of addresses, because the RFCs say that there can be more than
one address. $msg->sender returns (as documented) only ONE address.
So, in case there is no "Sender:" or "From:" field, the effective
action is  @from = (undef);

The best way to use sender:

  if(my $sender = $msg->sender)
  {   ....
  }


> my @from = $msg->from;
> my @from_address_list = ();
> if ($#from >= 0) {
>          foreach (@from) {
>                  push (@from_address_list, $_->address);
>          }
> }

This piece of code can be simplified a lot. Remember that a foreach with an
empty list is simply skipped.  So, this code become:

  my @from = $msg->from;
  my @from_address_list = ();
  foreach (@from) {
     push @from_address_list, $_->address;
  }

or

  my @from_address_list;
  foreach ($msg->from) {
     push @from_address_list, $_->address;
  }

or

  my @from_address_list = map { $_->address } $msg->from;

-- 
               MarkOv

------------------------------------------------------------------------
drs Mark A.C.J. Overmeer                                MARKOV Solutions
       [email protected]                          [email protected]
http://Mark.Overmeer.net                   http://solutions.overmeer.net