use Regexp::Common qw /net/;

# match dotted decimal IP address
# $1 = whole match, $2-5 = bytes
my $IP = $RE{net}{IPv4}{-keep};

foreach my $line (@connections) {
    if ($line =~ /^\s*$IP:\d+\s*->\s*$IP:\d+\s*->\s*$IP/x) {
       $client_ip{$1}{$iteration}++;
       $vips{$6}{$iteration}++;
       $frontend{$11}{$iteration}++;
    }
}