use strict;
use warnings;
use Getopt::Long;
use Data::Dumper;

my %options;
GetOptions(
    \%options,
    'length|height=i',
);

print Dumper \%options;

##</code><code>##

E:\>go.pl --height=1
$VAR1 = {
          'length' => 1
        };

E:\>go.pl --length=1
$VAR1 = {
          'length' => 1
        };