since you even used the word "configure", why not make a class variable, and have the Configure sub set that variable (or just write it directly)? You would have to have a lot more protection/error-checking than in this example, but the proof-of-concept could be:

package MyClass;
use warnings;
use strict;

our %Config;

sub Configure {
    %Config = %{$_[0]};
}

sub new {
    my $class = shift;
    my $self = {%Config};
    my %args = @_;
    foreach (keys %args) {
        $self->{$_} = $args{$_};
    }
    return bless $self, $class;
}


package main;
use warnings;
use strict;
use Data::Dumper;

MyClass::Configure( {group => 1, defined => 'values'});
my $x = MyClass->new();
my $y = MyClass->new(extra => 'here');
MyClass::Configure( {group => 2, defined => 0});
my $z = MyClass->new(third => 3);

$/ = "\n";
print Dumper $_ for $x, $y, $z;
[download]