[RndTbl] RegEx help needed (sed?)

I'm using sed to massage some input. Specifically, I have input lines like aaaaaaaaaa/BBBBB_ccc@00000 or aaaaaaaaaa/BBBBB@00000 and I want the output to always be BBBBB I've got most of it, but I can't figure out how to get rid of anything at the end of the line after EITHER the underscore OR the '@' (including either of those two characters). Is this possible in one expression in sed? I can do it with piping the input through sed twice but I was wondering if one pass would do it. Currently I'm using sed "s/^.*\/\(.*\)[_@].*$/\1/" Which doesn't get rid of the "_ccc" when it appears, just the "@00000". Suggestions?