use strict;
use warnings;

##</code><code>##

perl -c Whatever.pm

##</code><code>##

my $self = { $x => shift, $y => shift, $w => shift, $h => shift };

##</code><code>##

{ "" => $_[4] }

##</code><code>##

$ perl -e 'use Data::Dump; sub Box { my $self = { $x => shift, $y => shift }; dd $self } Box(qw{a b c})'
{ "" => "b" }