TL;DR

I tried out Imager::QRCode.

Overall, it does its job straight from the SINOPSYS:

use Imager::QRCode;
 
my $qrcode = Imager::QRCode->new(
    size          => 2,
    margin        => 2,
    version       => 1,
    level         => 'M',
    casesensitive => 1,
    lightcolor    => Imager::Color->new(255, 255, 255),
    darkcolor     => Imager::Color->new(0, 0, 0),
);
my $img = $qrcode->plot("blah blah");
$img->write(file => "qrcode.gif")
  or die "Failed to write: " . $img->errstr;

The size parameter is the size of each little tiny square representing a unit of information in the QR Code. I write this down because future me is going to get puzzled again by what Horizontal and vertical size of module(dot) means, possibly thinking that it has something to do with the overall size of the generated QR image.

One thing that makes me a bit uneasy is the upper limit for the data to be encoded. According to here, a full 177x177 8-bit image in High redundancy mode should be capable of holding up to 1273 octets, but I only managed to put 1268 in. Go figure.

Have fun!