If he wants visible watermarking then there are many ways to do it. Try looking at watermarker.com from some clues. Although I was involved in the field of steganography for some years as a researcher I have no personal experience with any Perl applications other than using PDL in our work.

Their is one CPAN module: Crypt::Mimetic which may help, but this is

If you do a goole search on "steganography perl" you will find some references to code which is out there and should be able to do your job with some adapatation - although the watermark will be invisible.

I have heard that Image Folio is useful as a complete suite for digital image assett management. A colleague also pointed out this post on the Image-Magick mailing list which referes to a Perl programme using Image::Magick for watremarking, I am not sure if it was visible or stego.

Good luck!

jdtoronto