my $img = Imager->new();
$img->open( file => '/path/to/tiff/file' );
my $color = Imager::Color->new("#000000");
my $font = Imager::Font->new(
    file    => '/path/to/ttf/font',
    color   => $color,
);
$img->string(
  text    => $stuff_to_write,
  x       => $x,
  y       => $y,
  font    => $font,
);