I just wrote a little multi-client server at work. It's in a request-response type of situation, i.e., the connections are short lived. Instead of forking, I used threads. One does need to share data explicitly. Some code samples are as follows: (any comments are appreciated, since it wasn't used in a heavy production environment, so I'm not sure how it scales.)

use strict;

use threads;
use threads::shared;
use IO::Socket;

# need to explicitly share variables across threads
our $something_to_share;
share($something_to_share);

my $socket = new IO::Socket::INET(
                  LocalPort=> 11023,
                  Proto => "tcp",
                  Listen => 10,
                  Reuse => 1)
    or die "Socket could not be created, reason: $!";

while( my $client  = $socket->accept() ){
    threads->new(\&handler, $client)->detach();
}

exit(0);

sub handler{
    my $client = shift;

        #read request.
    my $input = <$client>;

        # do something, probably access the
        # the shared variable $something_to_share;
        # and send response back.

    print $client "something for you.";
}
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