If you want to use named parameters, I suggest you use a named parameter parser. I have attached my version of the named (switched ) paramter parser as well as my version of the shapes module.

package NP;

require 5.00503;
require Exporter;

use strict;
use warnings;
use Carp;
use Data::Dumper;
use vars qw/ @ISA @EXPORT /;

@ISA = qw/ Exporter /;
@EXPORT = qw/ ParseNamedParameters /;


sub ParseNamedParameters
{
    my $allowed_parameters = shift;
    my @param = split /\|/, $allowed_parameters;
    my %param = ();

    return undef unless scalar @_; # must have something to decode fir
+st

    if (ref $_[0] eq 'HASH') {
        # Parameters passed in as HASHREF
        for my $p (keys %{$_[1]}) {
            if ($p !~ /^(?:$allowed_parameters)$/i) {
                print "Unknown parameter '$p', must be [$allowed_param
+eters]\n";
            } else {
                $param{'_' . lc $p} = $_[1]->{$p};
            }
        }
    } elsif ($_[0] =~ /^-(?=$allowed_parameters)/i) {
        # Parameters passed in as named parameters
        my (%p) = @_;
        for my $p (keys %p) {
            if ($p !~ /^-(?:$allowed_parameters)$/i) {
                print "Unknown parameter '$p', must be [$allowed_param
+eters]\n"
            } else {
                $param{'_' . lc substr($p,1)} = $p{$p};
            }
        }
    } else {
        for my $p (@param) {
            my $val = shift;
            $param{'_' . lc $p} = $val;
        }
    }

    return \%param;
}

1;


package shapes;
use NP;

sub new {
    my $class = shift || "shapes";
    my $self = {};
    bless $self, $class;

    my $allowed_parameters = "shape";

    # only decode parameters for the base object
    # derived objects have to decode their own parameters
    if ($class eq "shapes") {
        my $param = ParseNamedParameters($allowed_parameters, @_);
        @{$self}{keys %$param} = values %$param;
    }

    return $self;
}

sub print_shape {

   my $self = shift;
   print $self->{_shape}{line1} . "\n";
   print $self->{_shape}{line2} . "\n";
   print $self->{_shape}{line3} . "\n";
}

1;


#!/usr/bin/perl -w
use strict;
use lib "./";
use shapes;

my %box;
$box{line1} =  ' ---';
$box{line2} =  '|    |';
$box{line3} =  ' ---';

my $box = shapes->new(-shape => \%box);
$box->print_shape();
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