You don't give us much to work on. We need to see a minimal working piece of your code that produces this behaviour.

One thing that could possibly cause this behaviour could be some bad handling of the HTTP/1.1 connection, but very few clients speak HTTP/1.1 and get that wrong.

A second thing might be that you are writing the images to the client from your Perl script in one go - this is not how HTTP works.

So please post a small snippet of your Perl code that produces this behaviour.