http://www.perlmonks.org?node_id=84430
Description: This is code designed for controlling an HP printer using only IO::Socket, oh and interoffice war fare. I used it to "threaten" the global help desk. I told them that if I didn't get what I want (Access on a certain machine for a project that was two weeks past due because of their mess up) I'd make all of the printers at the world head quarters display $msg. *grin*

I know it's not pretty, but it works nicely for me

Update: I included a couple of the resources I used to figure out the PJL syntax and commands used in the script.

C-.

use IO::Socket;

my $host = 'INSERT IP HERE'; 
my $port = '9100'; #jet direct port
my $eoln = "\x0A";
$msg = 'Insert $0.25 and Press Go to Continue';

my $sock = IO::Socket::INET->new(PeerAddr => $host,
                                 PeerPort => $port,
                                 Proto => 'tcp');
die "Couldn't connect to $host on $port: $!\n" unless $sock;

print "Connected\n";
    $printer{"escapeseq"} = chr(27) . "%-12345X\@PJL";
    $printer{"input"} = "\@PJL OPMSG DISPLAY= \"$msg \" $eoln";
    $printer{"last"} = "\x1B&k3G";
    foreach $key (sort(keys %printer)){
    if ($key eq "escapeseq"){
        syswrite($sock, $printer{$key}, $len);
    }else{
        my $len = length $printer{$key};
        unless(syswrite($sock, $printer{$key}. chr(27), $len) == $len)
+ {
            $sock->close;
            print "Server unexpectedly closed connection\n";
            last;
        }
    }
}
HP site link 1

HP site link 2

and you can do a search on google for 12345x@pjl