Please, excuse typos, that code is writen directly to web form. Consider it as idea, not final code.

package FormValidator;
use strict;
use warnings;

my %conf;#{app_id1=>conf1,app_id2=>conf2}
sub new {
  my ($class,$conf,$app_id) = @_
  $app_id = $ENV{APP_ID} unless defined $app_id;
  $conf{$app_id} = $conf if defined $conf;
  return bless $conf{$app_id}, $class;
}
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The idea is to distinguish between applications using APP_ID, which can be set in apache configuration. If you want set configuration for some application, you can perform

#first application
$ENV{APP_ID} = 'APP_1';
my $obj_1 = FormValidator->new({foo=>'bar'});
my $obj = FormValidator->new();
print $$obj{foo};#prints 'bar'

#second application
my $obj_2 = FormValidator->new({foo=>'BAZ'},'APP_2');
my obj = FormValidator->new();
print $$obj{foo};#prints 'BAZ'
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