on *:invite:#:{ 
  if ($chan(0) == 30) {
    msg [Mega]swiftbot join $chan
  } 
}

and this 

on *:INVITE:#:{ 
  if ( $readini(cbl.ini,chans,$chan) == $null) { 
    join $chan
    msg $chan Invited by $nick // Hi, I am Swiftbot !commands for my commands !part swiftbot to make me leave if u need help join #swiftbot // Joins %joins [ $+ [ $chan ] ] //   
  } 
  else { 
    halt