You can't unpack variable length records like that (you say 'fixed length' in the title, but I'd call them variable if the first two bytes tell you how long the rest of the record is). You could read in the first two bytes, and then use that to read in the rest of the record using read.

Update: /me is corrected by jmcnamara in CB and goes to reread pack and the use of "/" in the template...though it still doesn't quite work for the OP.