my @myarray = undef;
    print "\@myarray contains ", 0+@myarray, " elements.\n";
__END__
Produces:
    @myarray contains 1 elements.

##</code><code>##

    @myarray = undef;

##</code><code>##

    @myarray = ( undef );

##</code><code>##

    undef @myarray;