=head2 hash

B<THIS MODULE IS EXPERIMENTAL>.  The interface to this module is pretty
much guaranteed to change in later versions of News::Gateway.  Don't rely
on the current interface.

This module provides a generic interface for loading hashes from disk
files.  It can transparently handle either regular files (which are loaded
into a memory hash) or Berkeley db files (which are tied to a hash
directly).  The following method is included:

=over 4

=item hash_open (FILE [, SPLIT])

If C<FILE> ends in F<.db>, then it will be tied directly to a hash.
Otherwise, it will be opened and its contents read into memory.  C<SPLIT>
is an anonymous code reference that will be called with each line and is
expected to return a list consisting of the key and then the value (or
values, if there are more than one associated with a key).  If C<SPLIT>
isn't provided, each line minus the trailing newline will be taken as a
key and the value will always be 1.

If C<SPLIT> returns more than one value for a key, the key will be
associated with an anonymous array containing all the values.  Otherwise,
the key will be associated with the value directly.

This method returns a reference to the resulting hash, or undef if the
file could not be opened.

=back