I would suggest building the required structure this way:

my @hostatt;

push @hostatt,  # Info for First host
    {
    'value' => 'some value1',
    'name' => 'URL',
    'arg2' => undef,
    'arg4' => undef,
    'arg1' => 'someurl.com',
    'arg3' => undef
    };

push @hostatt,  # Info for Second host
    {
    'value' => 'some value2',
    'name' => 'URL2',
    'arg2' => undef,
    'arg4' => undef,
    'arg1' => 'someur2.com',
    'arg3' => undef
    };
#Finally, assign this to the main structure
my $host = $ops->create_or_update_host(
    ip                  => 'nodename.com',
    name                => "Name",
    hostgroup           => { name => 'RDG - Prod Services' },
    hosttemplates        => [ { 'ref' => '/rest/config/hosttemplate/94
+', 
                                'name' => 'AA-RDG-Pseudo-services' } ]
+,
    hostattributes        => \@hostatt, #          <<< HERE <<<<<
   notification_period => { name => 'RDG-24x7-Minus-Bounce' }
);
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