Got this working with regex, however probably not the best way going forward. I'd like to use findstr or matchstr instead, but having some teething issues around that.
when STREAM_MATCHED {
log each match found by the stream filter
log local0. "Stream filter matched:[STREAM::match]"
set myvar [STREAM::match]
set 4 "blah"
regexp {Username=(.+)\sUserpassword=(.+)\sUseremail=(.+)\sUserhomefolder=(.+)\s} $myvar matched sub1 sub2 sub3
log local0. "Username=[b64decode $sub1] Userpassword=[b64decode $sub2] Usermail=[b64decode $sub3]"
}
when LB_SELECTED {
set serverIP [LB::server addr]
log local0. "LB Server IP $serverIP"
}