Hello again Monks!

Another day - another mystery. This time is about double bitwise negation (or strange form of smartmatch)

First encountered in DBM::Deep:

my %is_legal_filter = map {
    $_ => ~~1
} qw(
    store_key store_value
    fetch_key fetch_value
);
[download]

Than, in Devel::Declare (even stranger form):

  set_in_declare(~~@{$temp_name||[]});
[download]

Deparse says that at least first one is double negation, no-op. So - what for?

P.S. is the second example just a weird replacement for scalar ?