I'm also not sure I understand the motive for optimization at this point (2,3)-- it seems premature... but I will defer to your experience.

I am certain I haven't had any problems keeping my Ruby hashes and arrays separate (4)-- and those don't even have sigils (of course, a simple naming convention might keep them straight, but what a pain if you decide to switch an object from one class to another-- indeed, the Perl sigils have this same annoying property).

As to 5, I think I'll wait for Ex5, since I've not yet internalized A5, but I don't see how the brackets/brace is a problem if you are assigning a series of key/values to a hash. Larry appears to be proposing / %hash{key}:=(val) %hash{key2}:=(val2) / I don't think that / %hash['key']:=(val) %hash['key2']:=(val2) / would be any less acceptable or readable once the programmer gets used to brackets (and using literals instead of bare words). I certainly like the notion of having something like %hash = ($x =~ /key:=(val) key2:=(val2) / ) available, but I didn't see that in A5 (maybe I missed it?).