Add multiple inheritance support to Perl client (#1681)

* add multiple inheritance support to perl client

* remove allof test from fake petstore

samples/client/petstore/perl/t/ChildTest.t

@@ -0,0 +1,33 @@
+=begin comment
+
+OpenAPI Petstore
+
+This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+
+OpenAPI spec version: 1.0.0
+
+Generated by: https://openapi-generator.tech
+
+=end comment
+
+=cut
+
+#
+# NOTE: This class is auto generated by the OpenAPI Generator
+# Please update the test cases below to test the model.
+# Ref: https://openapi-generator.tech
+#
+use Test::More tests => 2;
+use Test::Exception;
+
+use lib 'lib';
+use strict;
+use warnings;
+
+
+use_ok('WWW::OpenAPIClient::Object::Child');
+
+my $instance = WWW::OpenAPIClient::Object::Child->new();
+
+isa_ok($instance, 'WWW::OpenAPIClient::Object::Child');
+