Do you mean to use $io->autoflush(1) ? Try this code: 
use strict; use warnings;
use IO::Handle;

open my $WHOIS, "whois x.x.x.x 2>&1 |";
my $io = IO::Handle->new;
$io->fdopen($WHOIS, "r");
$io->autoflush(1);
while(my $line = $io->getline){
    print $line;
}
$io->close;

[download]
This is working fine on my environment.

In reply to Re^3: Non-buffered read from program by myuji
in thread Non-buffered read from program by arc_of_descent

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