package Foo;

use strict;
use warnings;

my %defaults =
(
    -foo => "foo",
    -bar => "bar",
);

sub import
{
    shift;
    my %def = @_;
    $defaults{_normalise_key($_)} = $def{$_} for keys %def;
}

sub _normalise_key
{
    local $_ = shift;
    s/^-?(.*)/-\L$1/;
    $_
}

sub new
{
    my $class = shift;
    my $number = shift;
    my %args = @_;

    my %realargs = %defaults;

    for ( keys %args )
    {
        my $value = $args{$_};

        $realargs{_normalise_key($_)} = $value;
    }

    my $self = bless {}, $class;

    return $self;
}