Groovy Scripting : Set Attribute of Custom Field Based on the Value of Standard Field

In relation to my previous inquiry Groovy Scripting: Split / Trim, I have made it work. However, since formula text field cannot be displayed to OTBI analysis report, I am finding another way to show it to the report. I have created another custom text field and created a field trigger, but it is not working.

Trigger: After Field Changed

Field Name: Email

Script:

def position = Email.indexOf("@")

def email = Email.substring(0,position)

def CustomField = CustomField_c

if (ResourceOrgRoleName.contains('<role>')) {

setAttribute(CustomField, email)}

else null

The field has still no value. What might be possibly wrong or missing with the script? Or should it be an object trigger?