Form Hack question: parsing BBCode in variables

[IdealExchange]

I'm trying to edit the Form Hack mod such that it will parse BBCode and line breaks in the $formpurpose variable. I'll admit right now that while I do have a few years of programming experience under my belt, I'm quite new to PHP, so my apologies if this is a stupid question.

I have found that there is a function called bbcodeparse(), contained in functions.php, that does this. In order to use it, I must include global.php. So, I tried inserting the following code before the eval statement:

require('./global.php');
$formpurpose=bbcodeparse($formpurpose);

eval('print_output("' . fetch_template("$maintemplate") . '");');

No good; I get an undefined function error. So, newbie question though it may be, what am I doing wrong? Can someone show me the proper way to have Form Hack parse BBCode in the $formpurpose variable?

Your help is appreciated!