Using CAM::PDF, you can parse the document and find the string that corresponds to what you're looking for. As for how? I dunno. You might want to look at the source for Test::PDF which uses CAM::PDF to verify that two PDFs contain the same data and structure and see what stvn does there.
My criteria for good software:
Does it work?
Can someone else come in, make a change, and be reasonably certain no bugs were introduced?