#!/usr/bin/perl

use strict;

my @subs = qw(itchy.foo scratchy.bar homer.bab);

my @tmpl = ("To: webmaster\@DOMAIN",  "Dear Sir or Madam:", "You have won \$1,000,000!");

my ($sub, $str, $str_for_subbing);

for $sub(@subs) {
  open(FH,">virt.$sub") or die;
  
  # Assume @templ in your code should have been @tmpl 
  # -- good reason to use strict!
  
  foreach $str (@tmpl) {
    $str_for_subbing = $str;
    $str_for_subbing =~ s/DOMAIN/$sub/g;
    print "$str_for_subbing\n";
    print FH "$str_for_subbing\n";
  }
  close(FH)
}