=head2 function

C<function> can take various arguments as follows.

    $retval = function();
    $retval = function($arg);
    $retval = function($arg, \%arg_map);
    $retval = function($arg, \%arg_map, \@arg_list);

The arguments are:

=over 4

=item C<$arg>

A string denoting ...

The default is ...

=item C<%arg_map>

This is a hash of ...

...

=back

Missing arguments use the defaults shown.

The return value (C<$retval>) is always ...