#/usr/gnu/bin/perl -w
use strict;
my $file = "pathname/to/acl/user/file";
open (ACL,$file);
my @users = <ACL>;
close (ACL);

my $user;
foreach $user (@users) {
     chomp ($user);
     $user = "$user" . "\.mydomain\.com"; #add domain for smtp
     print $user; #to get a listing
     }