You seem to be a good enough programmer that you can probably get away with symbolic references in this case. (I tend to use the list of allowed variables too.)

I don't like the idea of encouraging beginning programmers to use them, however. It's a quick way to open up a security hole in a CGI script, and you don't get the protection of -w and strict. Worst yet, it lets beginning programmers tie themselves up in knots trying to make "var₁", "var₂", ... "var_n" when they should be using an array or a hash.

Programming well is hard enough without encouraging people to put on blindfolds, put raw meat down their pants, and dangle over an alligator pit. People like you and I, who know what we're doing (or can fake it convincingly) can get away with that sort of thing... but I'm not going to recommend it for someone who can't tell me what a typeglob is, for example.