• 1 - script is not executable. Try chmod +x success.pl on Unix. On windows, you need to invoke scripts via perl.exe (from $^X)
• 2 - system does not capture output
• 3 - There is no OPEN function. Did you mean open? Probably not. You would read the contents of success.pl, but not execute it.
• 4 - like system, exec does not capture output, and it replaces the current process with another process. You will never reach the following print statement. Either exec() fails and die terminates your script, or exec() is successful and replaces the process with your script with the new process running success.pl.

You should really start reading the perl documentation. You might be interested in do, require, perlmod.

Alexander