+# The INSTRUCTIONS
+#
+# The filters live in a directory tree of their own in $main::root/filter
+#
+# Each type of filter (e.g. spot, wwv) live in a tree of their own so you
+# can have different filters for different things for the same callsign.
+#
+# Each filter file has the same structure:-
+#
+# <some comment>
+# @in = (
+# [ action, fieldno, fieldsort, comparison ],
+# ...
+# );
+#
+# The action is usually 1 or 0 but could be any numeric value
+#
+# The fieldno is the field no in the list of fields that is presented
+# to 'Filter::it'
+#
+# The fieldsort is the type of field that we are dealing with which
+# currently can be 'a', 'n', 'r' or 'd'. 'a' is alphanumeric, 'n' is
+# numeric, 'r' is ranges of pairs of numeric values and 'd' is default.
+#
+# Filter::it basically goes thru the list of comparisons from top to
+# bottom and when one matches it will return the action. The fields
+# are the element nos of the list that is presented to Filter::it. Element
+# 0 is the first field of the list.
+#