+### scan
+
+ hook(type => "scan", id => "foo", call => \&scan);
+
+This hook is called early in the process of building the wiki, and is used
+as a first pass scan of the page, to collect metadata about the page. It's
+mostly used to scan the page for WikiLinks, and add them to `%links`.
+Present in IkiWiki 2.40 and later.
+
+The function is passed named parameters "page" and "content". Its return
+value is ignored.
+