Perl script to parse SNMP trap and set VarCustom01

I was trying the following script but I get no variable when trying to parse this way:

sub Main{

     $source = $Fields->{VarRawMessageText};

     my ($IP) = $source =~ /^\S+/;

     $Fields->{VarCustom01} = $IP;

     return "OK";

}

The VarRawMessageText should be the following: 127.0.0.1 1.2.131.24.14.1 etc etc

If I remove tags the agent_ip= is not that and the above regex should be correct but the script is not parsing it.  I am using 8.3 of Kiwi (I do intend to upgrade but it's a production box)

I created a rule to run this script in the action and then I am calling %VarCustom01 to forward as the originator IP.  The reason is I am forwarding SNMP traps from Cisco Prime to Kiwi and then to NCM.  (there's some crazy logic as to why)