a.pl

package Foo {
use Moose;
use Moose::Util::TypeConstraints;
use namespace::autoclean;
use Config::General 'ParseConfig';

subtype 'Adapter',
  as 'Str',
  where { /(:?shell|irc)/i };

has config => (
               is => 'ro',
               isa => 'HashRef',
               required => 1,
              );

has adapter => (
                is => 'ro',
                isa => 'Adapter',
                required => 1,
               );

has name => (
             is => 'ro',
             isa => 'Str',
             required => 1,
            );

sub run {
  my $self = shift;

  use Data::Dumper;
  print Dumper($self->config), "\n";
  print $self->adapter, "\n";
  print $self->name, "\n";
}

sub BUILDARGS {
  my ($class, %args) = @_;

  my %conf = ParseConfig($args{config});
  $args{config} = \%conf;
  return \%args;
}

__PACKAGE__->meta->make_immutable;
}

package main{
my $foo = Foo->new(
                   config => 'foo.conf',
                   adapter => 'shell',
                   name => 'hongbot'
                  );

$foo->run;
}