My esteemed colleagues, flexvault and zwon, highlight different elements of your problem. But don't go away mad... or disappointed. The issue with environment is critical to your script; asking questions that have rather more of a Perl nexus has much to do with the likelihood of getting future help here.

A script which merely invokes the shell is a lot like the individual who asks permission to ask a question in the Monastery's CB. Neither is much more than a way to inconvenience a few electrons for no good reason... and neither gets to the root of the problem.

And your entire shell script... or, rather, Sophos' shell script... could be rewritten in Perl ... or Python, in fact, in which case, your question might well be directed to those who specialize in that language.

If you opt to try to do so in Perl, please do come again: we'll be pleased to help you with pointers to training, references and tips when you get stuck. Bit we really do expect you to have a Perl question... and to show that you've made an attempt to work out your issues, yourself.