set load_path [<directory>[:<directory> …]]
This setting is used primarily by LOAD and WHICH (and thus the $which() function). If the client tries to access a file and cannot find it, it searches through each directory listed in the LOAD_PATH. It operates much like the PATH statement in Unix shells. The directories are searched sequentially.
To set the path to your home directory, and the client's script library:
/set load_path ~:/usr/local/irc/script
To add ~/my_irc to the path:
/eval set load_path ${load_path}:~/my_irc
The client will also obey the IRCPATH environment variable when first starting the client. It will override LOAD_PATH until the client is started completely (i.e. everything in the .ircrc has loaded).