I'd recommend to use POE or AnyEvent for your program. These packages will take care about low level details, so you should only write handlers for read/write events.

Update: here's the example that uses AnyEvent. Start without arguments for server, or specify hostname as argument for client.

use strict;
use warnings;

use AnyEvent;
use AnyEvent::Socket;
use AnyEvent::Handle;

my $port = 7777;
my $cv = AnyEvent->condvar;

if ( $ARGV[0] ) {

    # client
    tcp_connect $ARGV[0], 7777, sub {
        my ($fh) = @_
            or die "connect failed: $!";
        create_handle($fh, 1);
    };
}
else {

    # server
    tcp_server undef, 7777, sub {
        my ( $fh, $host, $port ) = @_;
        warn "Accepted connection from $host\n";
        create_handle($fh, 0);
    };
}

sub create_handle {
    my ($socket, $exit_on_close) = @_;
    my ( $shandle, $thandle );
    my $destroy = sub { 
        $shandle->destroy; 
        $thandle->destroy;
        $cv->send if $exit_on_close;
    };
    $shandle = AnyEvent::Handle->new(
        fh       => $socket,
        on_error => $destroy,
        on_close => $destroy,
    );
    $thandle = AnyEvent::Handle->new(
        fh       => \*STDIN,
        on_error => $destroy,
        on_close => $destroy,
    );
    $shandle->on_read( sub { 
        print $shandle->rbuf;
        $shandle->rbuf = '';
      }
    );
    $thandle->on_read( sub {
        $shandle->push_write( $thandle->rbuf );
        $thandle->rbuf = '';
      }
    );
}

$cv->recv;
[download]

Update: fixed some issues