perl-Data-OptList

Hashes are great for storing named data, but if you want more than one entry
for a name, you have to use a list of pairs. Even then, this is really boring
to write:

$values = [
    foo => undef,
    bar => undef,
    baz => undef,
    xyz => { ... },
];

With Data::OptList, you can do this instead:

$values = Data::OptList::mkopt([
    qw(foo bar baz),
    xyz => { ... },
]);

This works by assuming that any defined scalar is a name and any reference
following a name is its value.