define host{
    use windows-server
    ....
    }
    
define host{
    use windows-server
    }
is ok, BUT 
define host{
    use windows-server
    ....
    } 
define host{
    use windows-server
    }
is not ok!

##</code><code>##

#!usr/bin/perl -w
use strict;
use Data::Dumper;

my @DB;
my %hash = ();

while (<DATA>)
{
   if ( m/^define/.../}\s*$/)
   {
      next if /{\s*$/;
      next if /\s*\}\s*/;
      my ($hkey,$hval) = split;
      $hash{$hkey}=$hval;
   }
   else
   {
      push @DB, {%hash};
   }
}
push @DB,{%hash};

print Dumper \@DB;  #Array of Hash has been created

deleteDB ('address' => '192.168.1.1'); #delete one record

sub deleteDB 
{
   my ($key,$value) = @_;
   
   @DB = grep {$_->{"$key"} ne "$value"} @DB;
}

print "=============================\n";
print Dumper \@DB;

#Prints:
#$VAR1 = [
#         {
#            'use' => 'windows-server',
#            'hostgroups' => '060202',
#            'host_name' => 'serverA',
#            'address' => '192.168.1.1',
#            'alias' => '060202',
#            'contact_groups' => 'yu'
#          },
#          {
#            'use' => 'windows-server',
#            'hostgroups' => '060202',
#            'host_name' => 'serverA',
#            'address' => '192.168.1.11',
#            'alias' => '060202',
#            'contact_groups' => 'yu'
#          },
#          {
#            'use' => 'windows-server',
#            'hostgroups' => '060202',
#            'host_name' => 'serverA',
#            'address' => '192.168.1.21',
#            'alias' => '060202',
#            'contact_groups' => 'yu'
#          }
#        ];
#=============================
#$VAR1 = [
#          {
#            'use' => 'windows-server',
#            'hostgroups' => '060202',
#            'host_name' => 'serverA',
#            'address' => '192.168.1.11',
#            'alias' => '060202',
#            'contact_groups' => 'yu'
#          },
#          {
#            'use' => 'windows-server',
#            'hostgroups' => '060202',
#            'host_name' => 'serverA',
#            'address' => '192.168.1.21',
#            'alias' => '060202',
#            'contact_groups' => 'yu'
#          }
#        ];

__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
    }
    
define host{
    use windows-server
    host_name serverA
    hostgroups 060202
    alias 060202
    contact_groups yu
    address 192.168.1.21
    }