Maybe it would be a good idea to check the return value of ->send? The following program behaves as I expect, telling me that the remote end has closed the connection:

#!/usr/bin/perl
use IO::Socket;
my $sock1;

sub OpenSocket{
    $sock1 = IO::Socket::INET->new(
        PeerAddr => '192.168.1.99',
        PeerPort => 80,
        Proto    => 'tcp'
    );
    $sock1 or die "no socket :$!";
}

################ START SCRIPT #################

OpenSocket();
$str="Something to send";
while (1) {
    if( !$sock1->send($str)) {
        warn "Error: $! / $^E";
    };
}
close($sock1);
[download]

I'm not sure if the autodie pragma also covers IO::Socket. If it does, maybe you want to use it, if not, you will have to check every function call you make yourself for success/failure.