#!/usr/bin/perl

use strict;

$/ = "}";
while ( my $block = <DATA>) {
    print $block if ( $block !~ /\b\Q192.168.1.1\E\b/ );
}

__DATA__
define host{
    use windows-server
    host_name serverA
    hostgroups 060202
    alias 060202
    contact_groups yu
    address 192.168.1.1
}
define host{
    use windows-server
    host_name serverA
    hostgroups 060202
    alias 060202
    contact_groups yu
    address 192.168.1.11
}