The GD module is pure perl, although it does contain some code which needs to be compiled, and if you get a pre-compiled version then you don't even have to bother with that. Although the current GD doesn't support the GIF format any more due to patent issues, older versions will work fine if you have the correct libraries.

If you find GD a little tricky, then there's a spangly new alternative which doesn't require an external image library (although probably requires format specific libraries), which is Imager.

Although both these require some XS code at some point there's a very good reason for that - doing image manipulation with perl would most probably be prohibitively slow, but to be sure I guess there's one way of truly finding out: write the modules yourself.
HTH

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broquaint