I must have missed the deprecation announcement — you've quite surprised me.

$# is useful when you need an explicit index, eg., 0 .. $#arr . Sure, it's more perlish to avoid the index and iterate over the memebers directly, but sometimes you need this, for example when accessing two related arrays. (Yes, I know. If they're related then they may have been associated together in a list of hashes. Sometimes that's not appropriate though.)

In Perl 6, the .kv method operates on arrays too, yielding numeric indexes and values:

say "what is your favorite color?";
my @favorite_colors = ("blue", "red", "uhh, yellow!");
for @favorite_colors.kv -> $id, $color {
    say "$id. $color";
}
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