Synopsis:
   $currchans([<server refnum>])

Technical:
   Returns the current channels for each window connected to <server refnum>.
   If <server refnum> is -1, then $lastserver() is assumed. If no arguments
   are passed, all current channels are returned. This function returns
   each argument as "<server refnum> <channel>" in double quotes.

Examples:
   eval echo $currchans(1)    /* returns "1 #epic" "1 #unix" */
   (assuming there are two windows connected to server 1, with #epic in
    one window and #unix in the other)