On the other hand, that is exactly the point of a REPL (Read Evaluate Print Loop), like as perl -de1.
There is a time and a place for everything -- but times when you should eval unchecked user input are fairly rare rel to the number of times that it looks like it might be a good idea.
For example, interactive agents of mine often have an "evaluate this" command... but only if they are single-user, or first check if it is me.
Warning: Unless otherwise stated, code is untested. Do not use without understanding. Code is posted in the hopes it is useful, but without warranty. All copyrights are relinquished into the public domain unless otherwise stated. I am not an angel. I am capable of error, and err on a fairly regular basis. If I made a mistake, please let me know (such as by replying to this node).