C:\>type io.pl
use IO::Socket;
$|++;
my $sock = new IO::Socket::INET(
                   LocalHost => 'localhost',
                   LocalPort => 1234,
                   Proto     => 'tcp',
                   Listen    => SOMAXCONN,
                   Reuse     => 1 ) or die "no socket :$!";
while ($new_sock = $sock->accept()) {
    my ($buf, $char);
    while ( defined($char = $new_sock->getc) ) {
        print $char;
        $buf .= $char;
        do{process($buf); $buf = ''}  if $buf =~ m/END$/;
        exit if $buf =~ m/QUIT/;
    }
}

sub process { print "\nProcessing: $_[0]\n" }

C:\>io.pl
testing using: telnet localhost 1234END
Processing: testing using: telnet localhost 1234END
send data as a streamEND
Processing: send data as a streamEND
buffer input yourself and process as requireedEND
Processing: buffer input yourself and prosess as requireedEND
Hope that helpsQUIT
C:\>