my $spec = {
    'Parameters' => [
        'shipmentIncrementId' => {
            'required' => 1,
            'type' => 'string',
        },  
        'carrier' => {
            'required' => 1,
            'type' => 'ups|usps|dhl|fedex|dhlint|custom',
        },  
        'title' => {
            'required' => 1,
            'type' => 'string',
        },  
        'trackNumber' => {
            'required' => 1,
            'type' => 'string',
        },  
    ],  
    'Response' => 'scalar',
};

##</code><code>##

my @params = $thing->{'Parameters'};

for my $index (0..$#params) {
  next if $index % 2 != 0;
  my $parameter = $params[$index];
  my $spec = $params[$index + 1];
  # do something from here...
}

##</code><code>##

define_method 'foo' => {
  'Parameters' => [
    'bar' => {
      'required => 1,
      'type' => 'string',
    },
    'baz' => {
      'required => 1,
      'type' => 'string',
    },
  ]
};