if ( $line =~ m{
            ^\s*
            (                        # begin client IP
                \d+\.\d+\.\d+\.\d+
            )
            :\d+                     # client port (ignored)
            \s*->\s*
            (                        # begin vips
                \d+\.\d+\.\d+\.\d+
            )
            :\d+                     # vips port (ignored)
            \s*->\s*
            (                        # begin frontend
                \d+\.\d+\.\d+\.\d+
            )
        }x )
    {
        $client_ip{$1}{$iteration}++;
        $vips{$2}{$iteration}++;
        $frontend{$3}{$iteration}++;
    }