One way to execute possibly unsafe code is with Safe.

True, but I normally don't mention Safe because I think it's a little too easy to misuse. It requires a good amount of knowledge of the Perl internals, one must know not only which opcodes need to be allowed, but exactly what each one of them does; allowing only one too many can theoretically open a door for attackers. Plus, opcodes do sometimes change (rarely, but still), so that might have to be taken into account. Finally, the module currently appears unmaintained, and IIRC, has had some security-related bugs in the past. If used properly, Safe can make eval safer, but not "safe". That's why if there's any doubt, I'd recommend to not eval at all.