I've used eval string to good effect in a Perl script which acts as a sort of interpreter to run a program written in another language.
I used the eval so that I could simply translate the "OR" in this other language to "||", for example, leaving it to the eval to handle the syntax. I used a hash to contain the Other Program's variables and their values, for example, and then used those variable names in building the strings for eval to use. That kind of thing.
I was counting on the user using the Other Language's compiler (by the way, it's a compiled language) to ensure that the code was syntactically clean, before feeding it to my script.
Using eval in this instance meant not having to delve to a needless level of detail. Yes, laziness.