Well, I think I may have found my problem.
I made a quick little script to test the basic select function call against STDIN:

use strict;
use warnings;

my ($rin, $rout, $nfound);

$rin = '';
vec($rin, fileno(STDIN), 1) = 1;
$nfound = select($rout = $rin, undef, undef, 5);
syswrite(STDOUT, "We stop here...\n");
[download]

And I kept getting the same results, select returns immediately with nothing ready. So I decided that maybe it had something to do with the IO in the Windows NT console. So I copied that script over to my linux box (at home) and ran it there, and, well, it worked perfectly.
Which means I wasn't going crazy (good thing), but that I might not be able to do what I want to do (bad thing).
I did however write a very similar program in C that does work correctly, so I guess I will just have to write this in C.
Thanks for your help, --Glenn