Seems to have the same effect as API_JoinChannelByName.

Joins the channel with the specified name. A player can be in a maximum of 10 chat channels. In opposite to API_JoinTemporaryChannel the channel will be re-joined after relogging.

type, name = JoinPermanentChannel("channelName" [,"password" [,frameID[, hasVoice]]])

Parameters Edit

(copy/paste from API_JoinChannelByName)

Arguments Edit

channelName 

String - The name of the channel to join

You can't use the "-" character in channelName (patch 1.9)

password 

String (optional) - The channel password, nil if none.

frameID 

Number (optional) - The chat frame ID number to add the channel to. Use Frame:GetID() to retrieve it for chat frame objects.

hasVoice 

Boolean (1/nil) - Enable voice chat for this channel.

Returns Edit

type 

Number - The type of channel. 0 for a undefined channel, 1 for the zone General channel, etc

name 

String - The name of the channel (Ohklus: seems to be nil for most channels).

Example Edit

(copy/paste from API_JoinChannelByName)

JoinPermanentChannel("Mammoth", "thesane", ChatFrame1:GetID(), 1);