I've taken the liberty of correcting your typo. This is the most literal approach of what you've asked:

my $word = 'millennium';
{
    no strict 'refs';
    @$word = ();
}
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It's generally considered better form to use a hash, however.

my %arraysfromwords;
$arraysfromwords{ $word } = [];
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Of course, since split predates references in Perl, you may still be stuck.

Another option is to upgrade to a modern version of Perl with a working split, and use Inline::C. Since a string in C can be treated as an array of char pointers, all you have to do is to pass the SV to C, extract the string, create a new AV, and populate it with pointers to the new SVs representing each character.

I'd probably just use split though, and save myself thirty seconds.