I realize your regex wasn't meant to be used in a real example, but do realize that Perl will allow far more than \w chars in a variable. You can even get whitespace in there with symbolic refs:

$ perl -MData::Dumper -e '$field = "foo bar"; *$field = 1; print Data:
+:Dumper::Dumper(\%main::)'
$VAR1 = {
          # Cut other variables in output
          'foo bar' => *{'::1'},
        };
[download]

Of course, you could only access such a beast with another symbolic ref.