To expand a bit from OrFeAsGr, this should do what you want automatically whenever you connect to your channel, just replace the channel in the alias stream_channel


Code:
alias stream_channel return #channel
on *:connect:{
 if ($servertarget == tmi.twitch.tv) {
  if ($stream_on) {
    set %connect_stream 1
  }
  else .timercheck_stream 0 3 check_stream 
 }
}
alias check_stream {
  if ($stream_on) {
    if ($me ison $stream_channel) do_msg
    else set %connect_stream 1
    .timercheck_stream off
  }
}
on *:disconnect:{
  if ($servertarget == tmi.twitch.tv) unset %connect_stream
}

on me:*:join:$($stream_channel):{
  if (%connect_stream) {
   do_msg
  }
}

alias do_msg {
  msg $stream_channel this is just an example
}
alias stream_on {
  var %u = https://api.twitch.tv/kraken/streams/ $+ $mid($stream_channel,2)
  JSONOpen -ud stream_on %u
  if (!%JSONError) && ($json(stream_on,stream,_id)) return 1
}

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