Shouldn't that be the following?

my( $mail ) = Mail::DKIM::Verifier->new();
$mail->load( $raw_iohandle );
[download]

Because

my( $mail ) = load Mail::DKIM::Verifier->new();
[download]

is the same as

my( $mail ) = Mail::DKIM::Verifier->load->new();
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which passes no handle and no object to the load function.

Thanks. I figured I was piping it incorrectly. When you explained it I can see where I made my mistake. It is still either being interpreted incorrectly or I am really off somewhere as I cannnot get Mail::DKIM::Verifier to provide results as defined in the example. Here is my full code:

#!/usr/bin/perl

use strict;
use warnings;
use Data::Dumper;
use Email::Simple;
use Email::Simple::Creator;
use Email::Send;
use IO::Scalar;
use Mail::DKIM::Verifier;

use constant SENDER    =>    'test@circularbucket.com';
use constant SUBJECT    =>    'Email Message Report';


## Main 

# slurp the email from STDIN
my( $raw );
{ local $/ = undef; local *FILE; open FILE, "-"; $raw = <FILE>; close 
+FILE }

defined( $raw )
    or die( "Nothing read from STDIN!" );

# Create an IO::Handle for Mail::DKIM::Verifier to read message from
my( $raw_iohandle ) = new IO::Scalar( \$raw );

# Read from the IO::Handle
my( $mail ) = Mail::DKIM::Verifier->new();
$mail->load( $raw_iohandle );
$mail->CLOSE;

# Import message to Email::Simple
my( $incoming ) = Email::Simple->new( \$raw );





######################################################################
+##################################
# Message checks
######################################################################
+##################################

###############
# Are we spam?
my( $XSpamStatus ) = 0;
if ( $incoming->header( 'X-Spam-Status' ) =~ /^Yes.*score=([\S*])\s+/ 
+) {
    # we're spam, save the score
    $XSpamStatus = $1;
}

###############
# Check DKIM status
my( $result ) = $mail->result;

###############
# Gather who the message was from so we can send it back
my( $from_header ) = $incoming->header("From");

##############################
# Gather spam stats from the message
my $spam_stats1 = $incoming->header( 'X-Spam-Status' );

##############################
# Get SPF result from headers
my( $SPFStatus ) = 0;
if ( $incoming->header( 'Received-SPF' ) =~ /^pass.*/ ) {
    # we have a valid SPF record, so save the status
    $SPFStatus = 1;
}

##############################
# What MUA was used to send the message?
my $user_agent = $incoming->header( 'User-Agent' );






######################################################################
+####################################
# Generate the message to be sent back
######################################################################
+####################################
my( $body ) = <<BODY;

This is a test message. The test results will follow below.
-----------------------------------------------------------

BODY

if ( $XSpamStatus ) {
    $body .= "Message was scored as spam, with a score of $XSpamStatus
+\n";
}
else {
    $body .= "Message was not scored as spam.\n";
}



if ( $result ) {
    $body .= "Result1 was: $result\n";
}
else {
    $body .= "Result2 was: $result\n";
}


    $body .= "Return path was: $from_header\n";
    $body .= "Original test request was sent using: $user_agent\n";


if ( $SPFStatus ) {
    $body .= "\n\nSPF Record:     PASS\n";
}
else {
    $body .= "\n\nSPF Record:     FAIL\n";
}

foreach my $signature ($mail->signatures)
  {
      $body .= "signature identity: $signature->identity . \n";
      $body .= "verify result: $signature->result_detail . \n";
  }


my( $outgoing ) = Email::Simple->create(
    header =>    [
             From    =>    SENDER,
             To    =>    $from_header,
             Subject    => SUBJECT,
            ],
    body    => $body,
);
$outgoing->header_set( 'X-Processor' => 'email test script' );





######################################################################
+####################################
# Send the message back to the original sender
######################################################################
+####################################
my( $sender ) = Email::Send->new;
$sender->send( $outgoing );
[download]

Any nudges in the right direction are appreciated!

As you don't tell where exactly you get the errors, it's kinda hard to guess what might be going wrong.

• Standard input is already opened for your as STDIN, so

  # slurp the email from STDIN
  my( $raw );
  { local $/ = undef; local *FILE; open FILE, "-"; $raw = <FILE>; close 
  +FILE }
  [download]

  is an overly complex way of doing

  # slurp the email from STDIN
  my $raw; { local $/; $raw = <STDIN>; }
  [download]

• Why are you forcing a list assignment?

  my( $raw_iohandle ) = new IO::Scalar( \$raw );
  [download]

  should be

  my $raw_iohandle = new IO::Scalar( \$raw );
  [download]

  But then again, IO::Scalar is not nearly as robust as the native support for scalar handles added to 5.8

  open(my $raw_iohandle, '<', \$raw );
  [download]

• Finally, if the module expects a system file handle (e.g. if it attempts a child process to read from it), it'll be disappointed by your attempts since none of the Perl file handles you are producing have a system file handle associated with it.