ftp vip with multiple destinations based on user account

I'll knock up a much improved version shortly but this will suffice for now;

when CLIENT_DATA { 
    set user [regexp -inline {(?:USER\ )(\S+)} [TCP::payload]] 
     if { [string length $user] > 2 } { 
        if { [string match -nocase {s1.*} $user] > 0 } { 
            username started with s1, go to node 1
            pool FTP_prod_pool member 10.x.x.1 } 
        elseif { [string match -nocase {s2.*} $user] > 0 } { 
            username started with s1, go to node 1
            pool FTP_prod_pool member 10.x.x.1 } 
        elseif { [string match -nocase {s3.*} $user] > 0 } { 
            username started with s1, go to node 1
            pool FTP_prod_pool member 10.x.x.1 } 
        elseif { [string match -nocase {s4.*} $user] > 0 } { 
            username started with s1, go to node 1
            pool FTP_prod_pool member 10.x.x.1 } 
        else {
            username didn't start with s1-, must be s2-, go to node 2 
            pool FTP_prod_pool member 10.x.x.2 } 
     } 
     TCP::release
}