+ # Most servers will send a full nick!user@host prefix for
+ # messages from users. Therefore, when the prefix doesn't match this
+ # syntax it's usually the server hostname.
+ #
+ # This is not always true, though, since some servers do not send a
+ # full hostmask for user messages.
+ #
+ if prefix =~ /^(?:\S+)(?:!\S+)?@(?:\S+)$/