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Note that, because the C<Cycle> attribute receives its arguments in the
C<$data> variable, if the attribute is given a list of arguments, C<$data>
will consist of a single array reference; otherwise, it will consist of the
single argument directly. Since Tie::Cycle requires its cycling values to
be passed as an array reference, this means that we need to wrap
non-array-reference arguments in an array constructor:

    $data = [ $data ] unless ref $data eq 'ARRAY';

Typically, however, things are the other way around: the tieable class expects
its arguments as a flattened list, so the attribute looks like:

    sub Cycle : ATTR(SCALAR) {
        my ($package, $symbol, $referent, $attr, $data, $phase) = @_;
        my @data = ref $data eq 'ARRAY' ? @$data : $data;
        tie $$referent, 'Tie::Whatever', @data;
    }


This software pattern is so widely applicable that Attribute::Handlers::Clean
provides a way to automate it: specifying C<'autotie'> in the

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=head1 UTILITY FUNCTIONS

This module offers a single utility function, C<findsym()>.

=over 4

=item findsym

    my $symbol = Attribute::Handlers::Clean::findsym($package, $referent);

The function looks in the symbol table of C<$package> for the typeglob for
C<$referent>, which is a reference to a variable or subroutine (SCALAR, ARRAY,
HASH, or CODE). If it finds the typeglob, it returns it. Otherwise, it returns
undef. Note that C<findsym> memoizes the typeglobs it has previously
successfully found, so subsequent calls with the same arguments should be
much faster.

=back

=head1 DIAGNOSTICS