Every HTTP::Exception is a L<Exception::Class> - Class. So the same
mechanisms apply as with L<Exception::Class>-classes. In fact have a look
at L<Exception::Class>' docs for more general information on exceptions and
L<Exception::Class::Base> for information on what methods a caught
exception also has.

HTTP::Exception is only a factory for HTTP::Exception::XXX (where X is a
number) subclasses. That means that HTTP::Exception->new(404) returns a
HTTP::Exception::404 object, which in turn is a HTTP::Exception::Base -
Object.

Don't bother checking a caught HTTP::Exception::...-class with "isa" as it
might not contain what you would expect. Use the code- or
status_message-attributes and the is_ -methods instead.