Do you have Alt-O > IRC > Rejoin Channels on Connect checked?
As for your last paragraph, just search the internet for IRC clients. mIRC is the only one with decent scripting. As for the help file, the latest version has a CHM help file (CHM is modern). As far as being undocumented, I rarely run into trouble finding the answer to a question by looking in the help file and most veteran scripters will agree that it is the best resource for scripting. When you do run into a question, then this forum or a scripting channel are a great second resource. Finally, I'm not sure what you are referring to as far as variables. Variables are USER created and can't be documented by mIRC. %fun could store anything -- mIRC has no way to know, so cannot document it.