use Validate::Hash;
my $vh = new Validate::Hash(
            required => ['Fred', 'Wilma'],
            optional => ['Barney', 'Betty'],
            verify   => {Barney => qr/\d+/, 
                         Fred => qr/\w+/},
            -errs    => {illegal =>  "#KEY# is illegal",
                         required => "#KEY# is required!",
                         notmatch => 
                     "the value #KEY#, #VALUE#, doesn't match /#PATTERN#/",
            -strict => 1,
);

my %hash = (Fred => 'A', Barney => 1);

$vh->valid(\%hash); # returns false, 
$vh->get_error();   # returns 'Wilma is required!'