I'm not sure why you would want to split on word or non-word characters ([\w|\W]) instead of on an empty string:

$ perl -e 'print "$_\n" for split "", "foo"'
f
o
o
[download]

But, as GrandFather already pointed out, if you think you want to process a string character-by-character in Perl, then the odds are pretty good that you're doing it wrong.