In your on TEXT event, you can find the prefix in $rawmsg.
:nick!user@host PRIVMSG #chan :asdf
:nick!user@host PRIVMSG +#chan :asdf
:nick!user@host PRIVMSG @#chan :asdf
So something like $left($gettok($rawmsg,3,32),1) will return the prefix (or # if none was given in this example).