Bingo! That's the answer:
Note that argument processing varies depending on the number of arguments. If there is more than one argument in LIST, or if LIST is an array with more than one value, starts the program given by the first element of the list with arguments given by the rest of the list. If there is only one scalar argument, the argument is checked for shell metacharacters, and if there are any, the entire argument is passed to the system's command shell for parsing (this is /bin/sh -c on Unix platforms, but varies on other platforms). If there are no shell metacharacters in the argument, it is split into words and passed directly to execvp , which is more efficient.
(Thus saith system.)
Once the OP fixes his system usage, it may be worthwhile to go investigate Capture::Tiny. Rather than worrying about the portability issues that arise when dealing with the shell, leverage the power of CPAN by using Capture::Tiny. It's such a handy module, I wish I had found it several years ago.