Since this SIP2 has nothing to do with the more commonly known SIP, maybe Net::Protocol::SIP2_3M::Server

Note that all parts of a package name must be valid Perl identifiers. 3MSIP2 is not be cause identifiers must start with a letter or an underscore. Exception: Variable names may be all numeric digits, for example $1. Caveat: Variable names that are all digits are used by the regex expression match capture feature so there is a risk of their values being overwritten by the regex engine.