I support $singular and @plurals as a general convention. However, for hashes, I tend to think of hashes as providing a mapping function between a key and its value, so I frequently name it as a f() style, as in %last_name_for or %last_name_of or %has_subentries. That makes it clear to the reader that I'm holding a mapping in that hash.

-- Randal L. Schwartz, Perl hacker