Found it! From the archives (and tested):

use Image::Magick;

my $image = Image::Magick->new;
$image->Read("/tmp/test_in.jpg");
$image->Annotate(
        text=>"Hello, World!",
        font=>'sans-serif',
        fill=>'black',
        antialias=>'true',
        pointsize=>16,
        x=>10, y=>30,
    );
$image->Write("/tmp/test_out.png");
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