Or sometimes even just an array. The first time I thought I wanted to do this was 2003 and I was writing a perl script, and I was trying to loop through some sort of array, and write the outputs of some calculations to $val0 $val1 and so on, and I was neck deep into some horrible dark constructs like ${"val" . $i} before I actually realized that I really just wanted an array, you know, like the one I was already using.

It took me forever to understand map (the metafunction).