I have no strong preferences on _ref in those names. The issue that he mentions is not a problem for me because most of my variables have a small scope, so I'm unlikely to have 2 with the same name in scope. Lessening it even more, most of my hashes are references to hashes, so it is very unlikely that there is a hash or array to conflict with.

I also have no strong preferences on giving singular or plural names to arrays. Sometimes one looks right, sometimes the other.

I do have a strong preference that hashes get singular names, though.

The single most useful comment that I've seen on using hashes is, Think of a hash lookup as "of". That is, $age{'Sam'} should be read "age of Sam". Or, if you need it to be really unambiguous, $age_by_name{'Sam'} can be read "Age of whoever is named Sam."

This little recommendation fits every idiomatic use of hashes that readily comes to mind. When I was just starting Perl, it made it easy for me to spot where and when a hash would be useful, and decide what it should be called. With the benefit of experience I know of no better way to figure that out.

However that little linguistic principle that I treasure is ruined if you give hashes singularplural names. (Unless the values are array refs, in which case I would give it a plural name without even pausing to think about it.)

Update: Changed singular to plural per private note from hv.