Ok, so I think this is a bad idea:

• security-wise the use of string eval is nearly always risky, depending on the way you use the script of course, but I think it is a nasty habit anyway
• LISP tends to be completely interpreted, hence modifying the code at run time gives no added penalty, while Perl code is pre-compiled, which is a Good Thing (TM) for performance reasons. I hope it stays this way

Now that I think about it, if your eval was in a BEGIN block at least the eval syntax would be checked at compile time