To learn more about the perl system function, at your command line type
perldoc -f system

(to learn more about using perldoc, type 'man perldoc' at the command prompt).

Your problem is that system() is expecting a LIST of things you want done. You are providing it with two items which aren't even separated by a comma, so Perl is going crazy trying to figure out what you want.

Try system("ls -l") to provide system() with just one thing you want it to do. Same with exec. Be sure to perldoc -f exec to discover the differences between these two commands.