Sorry if I was confusing; I didn't mean you had to be in the directory. I just did it that way myself because I was lazy, and wanted to experiment with running the screensaver in a command ("cmd") window (so I only had to type the screensaver name, not the full path). But giving the full path is fine, and doesn't seem to conflict with the /s switch when I do it this way (note the space before the /s switch):

use strict;
use warnings;
system('C:/winnt/system32/sspipes.scr /s');
[download]

And yes, the "-w" part of the "shebang" line, as it's called, is for warnings (again, look at perllexwarn). The rest of the first line is more germane to Linux systems, where it specifies the path (ie. directory) where Perl is located (ie. "/usr/bin/perl"). But on Windows you can safely remove the entire first line, and the script should still run.