Hi there!
You can't use STDOUT as an input because as the name says it's only for output :) Instead open the file to an other FH (eg. FILE)

use strict;
use warnings;


my $cmd = 'd:\clwhois.exe';
my $ip = '192.168.1.1';
my $file = 'd:\temp\output.txt';

open(STDOUT, ">$file") or die "Can't open $file: $!\n"; # redirect STD
+OUT to a temp file

system ("$cmd $ip") and warn "Can not execute $cmd: $!\n";

close STDOUT;

open(FILE, "$file") or die "Can't open $file: $!\n";

while (<FILE>){
  print;
}

close STDOUT;
[download]

Hope that helps and if im mistaken please correct me

atnonis!