+plist <head pointer> [<data field to display>] [/<format>]
+end
+define countlist
+ set var $countlist_iter=$arg0
+ set var $countlist_count=0
+ while ($countlist_iter)
+ set var $countlist_iter=$countlist_iter->next
+ set var $countlist_count=$countlist_count+1
+ end
+ p $countlist_count
+end
+document countlist
+List elements counter iterating by `->next':
+countlist <head pointer>