It reads only the first line of the image.

This is not true. In the code line:

print <IMG>;
[download]

<IMG> is in list context. It should produce all the "lines" (by whatever definition of "line" $/ (the input record sepatator) gives - default separator is \n), then print should print all those elements joined by $, (the output field separator - by default undefined), followed by the content of $\ (the output record separator - also by default undefined).