Using ansible to append a string to the end of a line

I am using ansible to apply security hardening to CentOS6 VMs. We are following the 179 page CIS security benchmark:
http://benchmarks.cisecurity.org/downloads/show-single/?file=centos6.100

Thanks for the heads up to Philippe Eveque for the complicated regex and backrefs example:
https://groups.google.com/d/msg/ansible-project/JvHfchsgRaU/Vw_CzBbvadgJ

This code will add audit=1 to the end of any line starting with “kernel”

 - name: 4.2.3 Enable Auditing for Processes That Start Prior to auditd
   lineinfile: dest=/etc/grub.conf
               backup=True
               backrefs=True
               state=present
               regexp='(^\s+kernel(\s+(?!audit=1)[\w=/\-\.]+)*)\s*$'
               line='\1 audit=1'