IANA defines a long list of character-sets which can be used for any
internet communication, and to my surprise many of this list are not
understood by Encode::Alias.
My MailBox email processing automatically translates incoming message
bodies into "Perl's internal representation", and this sometimes fails.
Not too often, but sometimes.
The IANA list can be found at
http://www.iana.org/assignments/character-sets
The attached script shows the missing aliases. Maybe you can add at
least the simpelest definitions. Especially UNICODE-1-1-UTF-7, which
simply is UTF7 and used in some email RFCs.