Character not legal in expression?

iRule in question:

when CLIENT_ACCEPTED { ACCESS::restrict_irule_events disable } when ACCESS_POLICY_COMPLETED { set max_sessions 3 set apm_username [ACCESS::session data get session.logon.last.username] set apm_cookie_list [ ACCESS::uuid getsid "[PROFILE::access name].$apm_username" ] log local0. "[PROFILE::access name].$apm_username => session number [llength $apm_cookie_list]" if {[ACCESS::policy result] equals 'allow' [llength $apm_cookie_list] >= $max_sessions} { ACCESS::session remove ACCESS::respond 302 location "/vdesk/hangup.php3" } }