use strict;
use warnings;
use Data::Dumper;

my $str = 'May 16 11:17:12 system app: [id:id:id] Message [Class] [Priority:] {TCP} 111.1.1.64:1863 -> 222.2.2.155:55527';

# no need to use $1 $2 etc. when you can name them ;)
my ($mon,$day,$time,$app,$id,$msg,$proto,@ip) = 
   $str =~ /           # example match
      (\S+)\s+         # May
      (\S+)\s+         # 16
      (\S+)\s+         # 11:17:12
      ([^:]+):\s+      # system app
      (\S+)\s+         # [id:id:id]
      ([^\{]+)         # Message [Class] [Priority]
      (\{[^\}]+\})\s+  # {TCP}
      (\S+)            # 111.1.1.64:1863
      \s+\-\>\s+       #   (skip ->)
      (\S+)            # 222.2.2.155:55527
   /x;

print "$mon, $day, $time, $app, $id, $msg, $proto, @ip\n";