Using Exception::Class 

• An example from RT::Client::REST

use Exception::Class (
  'RT::Client::REST::OddNumberOfArgumentsException'   => {
    isa         => __PACKAGE__,
    description => "This means that we wanted name/value pairs",
  },

  'RT::Client::REST::InvaildObjectTypeException'   => {
    isa         => __PACKAGE__,
    description => "Invalid object type was specified",
  },

  'RT::Client::REST::MalformedRTResponseException'    => {
    isa         => __PACKAGE__,
    description => "Malformed RT response received from server",
  },
  # ...
);

• And later ...

RT::Client::REST::MalformedRTResponseException->throw(
  message => "Cound not read ID of the modified object",
);