%hash = (
    foo => 'bar',
    bar => sub { 'foo' }
);

(ref() eq 'CODE') && $_ = \$hash{ $_->() } for values %hash;

##</code><code>##

%hash = (
    foo => 'bar',
    bar => [ 'foo' ]
);

(ref() eq 'ARRAY') && $_ = \$hash{ $_->[0] } for values %hash;

##</code><code>##

%hash = (
    foo => 'bar',
    bar => 'REF:foo'
);

/^REF:(.+)/ and $_ = \$hash{$1} for values %hash;

##</code><code>##

%hash = ();
for (
    [ foo => 'bar' ],
    [ bar => \$hash{foo} ]
) {
    $hash{ $_->[0] } = $_->[1];
}

##</code><code>##

%hash = ();
%temp = (
    foo => 'bar',
    bar => \$hash{foo}
);

$hash{$_} = $temp{$_} for keys %temp;