With ircg_register_format_messages() you can customize the way your IRC output looks like or which script functions are invoked on the client side.
Plain channel message
Private message received
Private message sent
Some user leaves channel
Some user enters channel
Some user was kicked from the channel
Topic has been changed
Error
Fatal error
Join list end(?)
Self part(?)
Some user changes his nick
Some user quits his connection
Mass join begin
Mass join element
Mass join end
Whois user
Whois server
Whois idle
Whois channel
Whois end
Voice status change on user
Operator status change on user
Banlist
Banlist end
%f - from
%t - to
%c - channel
%r - plain message
%m - encoded message
%j - js encoded message
1 - mod encode
2 - nickname decode
See also: ircg_lookup_format_messages().