Can you spot the problem in your code below?

if ((($fileWidth gt $maxThumbSize) || ($fileHeight gt $maxThumbSize)) 
+|| ($retype eq "yes")) {
    if ($fileWidth gt $fileHeight) { $scalefactor=$maxThumbSize/$fileW
+idth; }
    else { $scalefactor=$maxThumbSize/$fileHeight; }
    $thumbWidth = int($fileWidth*$scalefactor); $thumbHeight = int($fi
+leHeight*$scalefactor);
}
else {
$thumbWidth=$fileWidth; $thumbHeight=$fileHeight;
}
[download]

You are comparing numeric values with gt. That means '6 gt 12' is going to be true. 'gt' and 'lt' compare string values, not numeric values, you should always use '<' and '>' instead to compare numeric values.

And also you can turn on binmode regardless of operating system. That will have no effect on Unix anyway, but will make a big difference under Windows.