my $array->[0] = $arg{key1};
my $key->[0] = 'key1' if ($array->[0]);

##</code><code>##


sub _sub {

my %arg = @_;

my $array;    # sometimes is treated as a scalar
$array->[0] = $arg{key1};
$array->[1] = $arg{key2};
$array->[2] = $arg{key3};
$array->[3] = $arg{key4};
...
}

##</code><code>##

_sub(key3 => 'big-mama');