Before I even try to figure out what your error is, I want to suggest you consider refactoring your code, at least in future programs.

Edit: I see you're using POE modules, which I don't use, nor have installed. I'll take a few more minutes to see if I spot anything, but I'm afraid I won't be able to run this.

For example, doing this:

if (...) {
   if (...) {
       if (...) {
           if (...) {
               .... 
           } else {
               return 0;
           }
       } else {
           return 0;
       }
   } else {
       return 0;
   }
} else {
    return 0;
}
[download]

If you reverse the logic, and do the return 0 blocks first, it's a heck of a lot easier to read and maintain:

    ($msg =~ /^([^\s]+)/) or return 0;
    $alias = $1;

    ($msg =~ /-address="([^"]+)"/) or return 0;
    $address = $1;

    ($msg =~ /-port="([^"]+)"/) or return 0;
    $port = $1;

    ($msg =~ /-nick="([^"]+)"/) or return 0;
    $nick = $1;

    ($msg =~ /-password="([^"]+)"/) or return 0;
    $password = $1;

    ($msg =~ /-prefix="([^"]+)"/) or return 0;
    $prefix = $1;

    ($msg =~ /-auto_connect="([^"]+)"/) or return 0;
    $auto_connect = $1;
[download]

You could even take it a step further, and make it data-driven. It's not as short as the first rewrite, but it has the advantage of grouping functionality together, so you can see what's being matched all in one section, and what's being assigned to in another section:

   # Regular expressions to apply
   my $a_regexes = [
       qr/^([^\s]+)/,
       qr/-address="([^"]+)"/,
       qr/-port="([^"]+)"/,
       qr/-nick="([^"]+)"/,
       qr/-password="([^"]+)"/,
       qr/-prefix="([^"]+)"/,
       qr/-auto_connect="([^"]+)"/,
   ];

   # Construct an array of resulting regex captures
   my @results = ( );

   # Save each pattern (returning if missing from regex)
   foreach my $regex (@$a_regexes) {
       if ($msg !~ /$regex/) {
           return 0;
       }
       push @results, $1;
   }

   # Assign to the desired variables
   my ($alias, $address, $port, $nick,
       $password, $prefix, $auto_connect) = @results;
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Update 2:

Here's an even terser suggestion for capturing the tokens, since (other than the first regex) they all have the same essential format. Define the list of tokens to capture, and build each regex from that:

   # Define the tokens we wish to extract
   my @tokens = qw( address port nick password prefix auto_connect );

   # First token is a special case
   my $alias = ($msg =~ /^(\S+)\s*/)? $1: "";
   $alias or return 0;

   # Construct an array of resulting regex captures
   my @results = ( );

   # Construct the regex from each token, and capture the value
   foreach my $token (@tokens) {
      ($msg =~ /-${token}="([^"]+)"/ or return 0;
      push @results, $1;
   }

   # Assign to the desired variables
   my ($address, $port, $nick, $password, $prefix, $auto_connect) = @r
+esults;
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