Is it better not to use a literal string as the first argument to split(), especially when demonstrating functionality to new users? Yes.

Is that functionality likely to be omitted from Perl 6? Possibly, unless that means forcing people to do silly things like this:

$pattern = qr/[:|]/;
@array = split $pattern;

# instead of

$pattern = '[:|]';
@array = split $pattern;
[download]

Is it officially deprecated? No.

Is it valid Perl? Yes.

Should someone vote down this whole friggin' thread? Yes, please.