Though theoretically feasible, a GIF to JPG converter written entirely in Perl would be too slow and likely suck up too much memory at runtime to be of any usefulness. Such computationally intensive tasks are better left to the likes of C.

You should look on you target machine to determine whether there's anything you need installed and/or do the conversion in some other way. Maybe you can download all the files to some other machine, convert them and then upload the converted files; this is the kind of task that's easy to automatize in Perl.