Your calling syntax is not incorrect, and the parts that we're seeing are not in disagreement with how Adobe reader is intended to be called. So since we know it's not a problem with the Perl code you've shown, that leaves four questions that I can think of:
- What does $outname contain?
- What is the cwd for your script.
- What is the absolute path to your PDF file?
- Does your script have read permission for that PDF?
You might be specifying a relative path that doesn't lead where you want it to when the script runs. Or your script might not have the correct permissions for the PDF.