To do this with any level of safety ; you would have to know more perl then John Galt to figure how to check the code for bad mojo.
This is super sketchy. You are basically blindfolding yourself, walking into the bronx with your pants to your ankles and your hands cuffed, with a sign on your back that says "please *#6!%^^ me in the -*# #^#_ and take my $$$$"

I would suggest to set up a sepparate box appart from your server to do this. Make a user called "beatme", "l3pp3r", or "thepoor"- and take away all the priviliges but running perl on that account. Maybe set up a sepparate error log for that user.

This box would be sent the text, and send back output. Hey, maybe you could have your own tail -f /var/log/httpd/error_log that refreshes - that would be cool.

Maybe people would have to send you some info before they can use it? Like their ssn and a copy of their driver's license? :)