Much appreciated Monks. You still haven't let me down yet.

This might not be the best method/code, but here's how I got it working. Any improvements welcome (I don't know why I have to use open twice, if I never close FILE, but it doesn't work otherwise):

my $file = 'd:\PROGRA~1\Syslogd\Logs\syslog22Dec2003.txt';

open (FILE, $file) or die "Can't open $file: $!\n";
my %messages;  

while(<FILE>) {
    /(FW\-\d+\-\d+)/;              # extract MSG ID
    next if exists($messages{$1});   # ignore it if we've
    $messages{$1} = $1;             # already seen it.
}


my $count;

open (FILE, $file) or die "Can't open $file: $!\n";

for my $i (keys %messages){
  print "\n$i:\n\n";
  $count = 0;
   while(<FILE>){
     if (/$i/){
    print "$_\n";
    $count++;
     }
    last if $count == 1;
   }
}

close FILE;
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