If you are trying to actually send out the /msg command on INIT, then use this:
Code:
on *:dialog:seenscript:init:0:{
  msg g seen %seenchans %seennicks
}

However, as _D3m0n_ said, it's probably unlikely that "g" will accept a string of channels followed by a string of nicks and then match them all up. You will most likely have to send them channel/nick combinations yourself and wait for the reply for each command before issuing the next request. That would just be a series of on NOTICEs or on TEXTs, depending on the format "g" uses to respond to your seen requests.

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