+Then, specify the refile rule. The refile target folder of auto
+refiling is decided by the value of @code{wl-refile-rule-alist}.
+@code{wl-refile-rule-alist} is a list of a rule:
+
+@example
+@group
+(@var{field} (@var{regexp} . @var{target})
+ (@var{regexp} . @var{target})
+ @dots{})
+@end group
+@end example
+
+Each rule means `if @var{field} value matches @var{regexp},
+then refile to @var{target} folder'.
+The rule matched first is applied.
+
+@var{field} is a string of field name. You can specify a list of field name
+string, too. In this case, if one of these fields is matched, then the
+rule is fired (i.e. OR condition).
+
+@var{regexp} is a regular expression for field value. @var{target} is a target
+folder string. You can specify a rule at @var{target} part, too. In this
+case, If the field value of the rule and the current rule is matched,
+then the current rule is fired (i.e. AND condition).
+
+In @var{target} part, you can refer matched substring of @var{regexp}.
+To refer substring, specify following in @var{target}:
+
+@table @samp
+@item \&
+means substitute original matched text.
+
+@item \@var{N}
+means substitute what matched the @var{N}th `\(@dots{}\)'.
+(@var{N} is a number.)
+@end table
+
+Following is an example of @code{wl-refile-rule-alist}.