Also in the code the line below will cause an error to be thrown saying "Useless use of string in void context at test.pl line XX."

That's a warning, not an error.

What you have to understand is that eval { block here } and eval EXPRESSION are two fundamentally different things. The first one is like do { ... }, except that it catches excpetions (other languages call that try. do { "something" } warns because "something" doesn't serve any purpose, because it's not used anyway.

So you just want eval $Your_string_here.

Update: Forgot the links to the docs: eval.