I think that you want to reorganize an array of hashes into a hash of arrays.

use strict;
use warnings;
use Data::Dumper;
my @servers = (
    { Host => 'server02', GroupName => 'serversA' },
    { Host => 'server04', GroupName => 'serversA' },
    { Host => 'server02', GroupName => 'serversB' },
    { Host => 'server04', GroupName => 'serversB' },
    { Host => 'server02', GroupName => 'serversC' },
    { Host => 'server04', GroupName => 'serversC' },
    { Host => 'server02', GroupName => 'serversD' },
);

my %consolidated;

foreach (@servers) {
    push @{$consolidated{$_->{Host}}}, $_->{GroupName};
}

print Dumper(\%consolidated);
[download]

OUTPUT:
$VAR1 = {
          'server02' => [
                          'serversA',
                          'serversB',
                          'serversC',
                          'serversD'
                        ],
          'server04' => [
                          'serversA',
                          'serversB',
                          'serversC'
                        ]
        };
[download]