But I think the existance of Tk::JPEG should be optional, e.g. with these lines:

eval q{ use Tk::JPEG }; warn "No JPEG support" if $@;
eval q{ use Tk::PNG  }; warn "No PNG support"  if $@;
eval q{ use Tk::TIFF }; warn "No TIFF support" if $@;
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with ot without the warnings...