line-structure

sender matches .+!.+@.+
colon is a literal :
command is just alphanumeric (typically PRIVMSG, JOIN, or QUIT)
target is either a nick or a channel
a nick is nonwhite
a channel is nonwhite, typically beginning with a #
text is anything except a newline
typical line: colon sender command target colon text

hostname usuall looks like alphanum.alphanum.alphanum but I've also seen just "services."
server greeting line: colon hostname digits nick stuff

notice line: colon (hostname or sender) NOTICE target colon text

ping line: PING colon hostname
notice line: NOTICE nonwhite colon stuff
join line: colon sender JOIN colon target
kick line: colon sender KICK target target colon stuff
mode line: colon sender MODE target flags
nick line: colon sender NICK colon stuff
part line: colon sender PART target
quit line: colon sender QUIT colon stuff
topic line: colon sender TOPIC target colon stuff