#!/usr/bin/perl -pw

use strict;
use warnings;

our ($prev1, $prev2);

if (/DISK.*DISK/) {
    if ($prev1 =~ /cache/ && $prev2 =~ /cache/) {
        print "\n";
    }
}

if ($prev1 =~ /DISK.*DISK/) {
    print "\n";
}

$prev2 = $prev1;
$prev1 = $_;