in reply to Is there perl script virus spyware malware?

I understand your question as how to identify Perl code that does bad things, not as how to check for viruses/malware in other files from a Perl script.

To that my answer to your question will be: "Read the code, Luke". Additionally you could put the code you don't trust enough in a Safe, define what things shall be considered "bad" and see if the code tries to do one of these bad things.