has 'ip_address' => (
	 is => 'ro',
	 isa => 'Str',
	 lazy => 1,
	 builder => 'get_ip_address',

...

  sub get_ip_address {
	 my $self = shift;
	 my $allclasses_file = $self->allclasses_file;
	 my $ip_address;

	 if ( $allclasses_file =~ m/_([^_]+$)/ ) {
		$ip_address = $1;
		return  $ip_address;
	 }
  }