I'm not sure, but I think it works along the same lines as $_, a scalar that's filled with the line as the while loop iterates over the file. This is just an assumption, but I think you can't stuff into an array or hash slice.

If you put the following into your code:

print *MF;
print "\n";
print $opt{'M'};
[download]

you'll see that the variables have the same content (unless there's some metadata controlling that), so it appears that the filehandle is being copied into the hash. I think your problem lies in the while loop, but I'm not sure yet why that is.

Update: from perlsyn:

The while is evaluating whether or not the hash or array has something in it. It's not evaluating the fileglob inside.

John J Reiser
newrisedesigns.com