Along similar lines, I will often create a hash of keys which are needed for lookup. For example, I will do:

my %acceptable_server = map { $_ => 1 } qw(
    DEV
    QA
    PROD
);
[download]

It's a nice way of working with a changing list of static acceptable things.

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We are the carpenters and bricklayers of the Information Age.

The idea is a little like C++ templates, except not quite so brain-meltingly complicated. -- TheDamian, Exegesis 6

Please remember that I'm crufty and crochety. All opinions are purely mine and all code is untested, unless otherwise specified.