Thanks Tye, oiskuu and others, for midwifing my first server code example.

Here is the final, working code. It correctly handles the initial connection and the client closing the connection, or being killed.

# server

use Modern::Perl;
use EV;
use AnyEvent;
use IO::Socket::INET;
my $is_connected;
my $project = my $config = my $text = my $this_engine = {} ;
$config->{remote_control_port} = 57000;

start_remote();
EV::run();
sub start_remote {
    my $port = $config->{remote_control_port};
    say "Starting remote control listener on port $port";
    $project->{remote_control_socket} = IO::Socket::INET->new( 
        LocalAddr     => 'localhost',
        LocalPort     => $port, 
        Proto         => 'tcp',
        Type        => SOCK_STREAM,
        Listen        => 1,
        Reuse        => 1) || die $!;
    start_watcher();
}
sub start_watcher {
    $this_engine->{events}->{remote_control} = AE::io(
        $project->{remote_control_socket}, 0, \&process_remote_command
+ )
}
sub remove_watcher {
    undef $this_engine->{events}->{remote_control};
}
sub process_remote_command {
    if ( ! $is_connected++ ){
        say "making connection";
        $project->{remote_control_socket} =
            $project->{remote_control_socket}->accept();
        $this_engine->{events}->{remote_control} = AE::io(
            $project->{remote_control_socket}, 0, \&process_remote_com
+mand );
    }
    my $input;
    eval {     
        $project->{remote_control_socket}->recv($input, $project->{rem
+ote_control_socket}->sockopt(SO_RCVBUF));
    };
    $@ and say("caught error: $@"), reset_socket(), return;
    logpkg('debug',"Got remote control socketput: $input");
    eval {
        $project->{remote_control_socket}->send(process_command($input
+));
    };
    $@ and say("caught error: $@"), reset_socket(), return;
}
sub reset_socket { 
    undef $is_connected;
    undef $@;
    $project->{remote_control_socket}->shutdown(2);
    remove_watcher();
    start_remote();
}
sub logpkg { say join " ", @_ }
sub process_command { "processed: ". shift } 

# client script

use Modern::Perl;
use IO::Socket::INET;
my $tcp = IO::Socket::INET->new( PeerAddr => 'localhost', PeerPort => 
+'57000', Proto => 'tcp', Type => SOCK_STREAM) || die $!;
    my $cmd = 'eval $this_track->name';
    do_remote_cmd($cmd);
    do_remote_cmd("greetings");
    do_remote_cmd("earthlings");
    do_remote_cmd("take me....");
    $tcp->shutdown(2);

sub do_remote_cmd {
    my $cmd = shift;
    $tcp->send($cmd);
    $tcp->recv(my $result, 65536);
    say "command: $cmd, result: $result";
}
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