Thanks for you comments and fixes .. however I can only see one thing that is changed (other than the addition of CLI code).

You've called pdfimageobj on the old pdf rather than the new one. That's wrong -- you need to call it on the new file, so that the page is loaded into the new pdf. The gfx->pdfimage call later then tells where that page should be placed.

You can tell that by the interface: You code ($img = $oldpdf->pdfimageobj($oldpdf, $pg)) would set @_ in the sub to ($oldpdf, $oldpdf, $pg). That wouldn't be right. There's be no need to declare the $oldpdf as a parameter to the sub as it's the object on which it's being called.