By newbies I don't mean people who've learned to program Pascal yesterday, but rather programmers from other languages who don't yet grok the concepts of runtime evaluation and code generation.
Thanks for the example, but it's not what I'm looking for. Your example is very idiomatic to Perl, I'd say it's a patch on a deficiency, because I have no trouble imagining tr/// implemented in such a way that allows the trick without eval.
What I'm looking for is more in the code-generation league. Generate some code with eval, on the fly, and call it when necessary.