A quick-and-dirty fix could be to keep each "seen" email address as a key in a hash (which could get very large, but hey--).

This could get you going:

#!/usr/bin/perl
use Email::Find;

my %seen_emails;  # this could get big!
$file = shift;
open (FILE, $file) or die "Couldn't open filename: ";
while (<FILE>)
{
 $text = $_;

 my $finder = Email::Find->new(sub 
 {
     my($email, $orig_email) = @_;
     my $formatted_email = $email->format;
     if (!defined($seen_emails{$formatted_email})) {
          # remember we've seen this guy
          $seen_emails{$formatted_email} = 1;
          
          # and show this email addy
          print $formatted_email . "\n";
     }
     return $orig_email;
 });

 $finder->find(\$text);

(this code is untested)

--twerq