I tried the Image::Magick module a while ago but never got it working. You can use ImageMagick directly though, without the module -- it comes with a bunch of utility programs. I found an old resizing script of mine that uses "mogrify.exe". Here's part of the script:

$ENV{'PATH'} = "C:\\Program Files\\imageMagick;" . $ENV{'PATH'};
# ...
for my $file (@files)
{
    $fileNumber++;
    my $newFile = "$largeDir\\$basename$fileNumber.JPG";
    print "$fileNumber copying $file...\n";
    copy("$originalDir\\$file", $newFile);

    open(INFO, "identify $newFile |");
    my $info = <INFO>;
    close INFO;
    my ($width, $height) = ($1, $2) if ($info =~ /\s(\d+)x(\d+)\s/);

    my ($newWidth, $newHeight, $thumbWidth, $thumbHeight);
    if ($width == 1200 && $height == 1600)
    {
        ($newWidth, $newHeight) = (600, 800);
        ($thumbWidth, $thumbHeight) = (98, 130);
    }
    elsif ($width == 1600 && $height == 1200)
    {
        ($newWidth, $newHeight) = (800, 600);
        ($thumbWidth, $thumbHeight) = (130, 98);
    }
    else
    {
        ($newWidth, $newHeight) = (600, 600);
        ($thumbWidth, $thumbHeight) = (98, 98);
    }

    my $newDimensions = $newWidth . 'x' . $newHeight;
    my @command = ('mogrify',
                   '-quality',
                   '100',
                   '-geometry',
                   $newDimensions,
                   $newFile);
    print "mogrifying $newFile...\n";
    system(@command);
[download]

(Note: I've only used this code with a version of ImageMagick that I downloaded 4 or 5 years ago.)

-Joe