The P:Line is a line in an ircd's configuration which allows the administrator to set up which ports the IRC Server will reside on...

P:accepted hostmask:*:*:port

In cyclone at least, there's also (in no particular order) a K:Line, Q:Line, C:Line, N:Line, X:Line, A:Line, M:Line, Y:Line, I:Line, U:Line, L:Line, H:Line and a O:Line. There's also a G:Line