Running your script manually worked for me. The file output.txt is in the directory from where I executed c:\perl\bin\perl.exe "d:\scripts\test.pl. I am not sure where the scheduler would place your output.txt so I advise to set a directory within your code (make sure you have proper permissions for the directory:

use strict;
chdir "c:/Users/Admin";
my $fname = "output.txt";
#open OUTPUT, ">$fname" or die "$fname: $!\n"; is more common but you 
+will miss the message when run by scheduler
unless(open(OUTPUT,">$fname")) {
    exit
}
print OUTPUT "This worked\n";
close OUTPUT;
[download]

You can use File::HomeDir to find your home direcory.It is in the ppm repository.