Some versions of GD (don't know if newer or older) seem not to have the class method trueColor(), so there an error arises. Therefor, I always pack the trueColor call into an eval:

eval { GD::Image->trueColor(1) };
if ($@) {
   # e.g. write to log that this method is not existing
}
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Best regards,
perl -e "s>>*F>e=>y)\*martinF)stronat)=>print,print v8.8.8.32.11.32"