I don't think it's a good idea to change Perl, because the interpolation rules are very basic and you would affect (=break) _a lot_ of other things. If somebody wants to use Perl, he/she should try to understand the very basics and if your beginners are unable to figure out that bit of concatenation, which i don't believe, they're absolutely not to be confronted with a programming language at all.

You _could_ instead of $machine have a magic %machine hash that via tie()ing invokes methods on FETCH:

"some string with $machine{work_dir} in it"
[download]

But this is a workaround, i believe it's easier to explain the simple syntax than to write that TIEHASH-module (which isn't too hard itself).

--
http://fruiture.de