iRule regex to normalize phone numbers?

OK, two steps got it to work.

Code
when  ACCESS_POLICY_AGENT_EVENT {
       expr srand([clock clicks])
       set otp [string range [format "%08d" [expr int(rand() * 1e9)]] 1 6 ]
       set mail [ACCESS::session data get "session.ldap.last.attr.mail"]
       set mobile [ACCESS::session data get "session.ldap.last.attr.mobile"]
       set mobile2 [string map {"." "" " " "" "-" "" "(" "" ")" "" "+" ""} $mobile]
       ACCESS::session data set session.user.otp.pw $otp
       ACCESS::session data set session.user.otp.mobile $mobile2
       ACCESS::session data set session.user.otp.username [ACCESS::session data get "session.logon.last.username"]
}