[slunk]

You've gotten a couple responses making arguments that the atoms required for a language like lisp are fundamentally simpler than eval in Perl and that makes the difference... Fwiw, I don't find these arguments very compelling. It's not so much that they're entirely false, but the "most beautiful program ever written [sic]" that we're talking about here is "beautiful" precisely because it elides all these "simple" details. I do get the vague sense that it is essentially a more verbose `eval $1`.

[mojuba]

I agree. You could probably say though, that once you decide to implement anything that's not `eval $1` you jump to the next level that forces you to parse the input and then use your built-in primitives to implement themselves. I think any minimal interpreter for any dynamic language will probably end up being pretty simple, though not necessarily as elegant as Lisp's. But elegance aside, there's nothing groundbreaking here.