package Foo::Exceptions; use strict; use warnings; use Exception::Class ( 'Foo::Exception::DBI' => { description => 'DBI Error', # error => $DBI::errstr, }, 'Foo::Exception::DBI::Dupe' => { description => 'Duplicate key', isa => 'Foo::Exception::DBI', # error => name of duplicate key, }, 'Foo::Exception::Dupe' => { description => 'Duplicate entry', fields => [ 'name' ], # error => value of duplicate field }, # etc. );