Raw
From Scriptwiki
Sends any parameters you supply directly to the server.
/raw [-q] <command>
You must know the correct RAW format of the command you are sending. Useful for sending commands which mIRC hasn't implemented yet.
The -q switch makes raw work quietly without printing what it's sending.
Note that it is the same as /quote.
Example
raw PRIVMSG #help.script :moo
This will send "PRIVMSG #help.script :moo" to the server. This example is the same as "msg #help.script moo".
See Also
You can also use /quote.
To learn more about the syntax, take a look at the IRC RFC (http://www.ietf.org/rfc/rfc1459.txt?number=1459).